Methods and devices for soft tissue dissection

ABSTRACT

An instrument for differentially dissecting complex tissue is disclosed, comprising a handle, a central longitudinal axis, and an elongate member, with a differential dissecting member (DDM) configured to be rotatably attached to a distal end. The DDM comprises at least one tissue engaging surface, a first torque-point disposed to a first side of an axis of rotation, and a mechanism configured to rotate the DDM around the axis of rotation, causing the tissue engaging surface to move in at least one direction against the complex tissue. The mechanism comprises at least one force-transmitting member attached to the first torque-point member and to a motive source configured to oscillate the DDM. The tissue engaging surface is configured to selectively engage the complex tissue such that it disrupts at least one soft tissue in the complex tissue, but does not disrupt firm tissue in the complex tissue.

PRIORITY APPLICATIONS

The present application is a continuation-in-part application of, andclaims priority to, U.S. patent application Ser. No. 13/872,766,entitled “Instruments, Devices, and Related Methods for Soft TissueDissection,” filed Apr. 29, 2013, which claims priority to: U.S.Provisional Patent Application No. 61/687,587, entitled “Instrument forSoft Tissue Dissection,” filed on Apr. 28, 2012; U.S. Provisional PatentApplication No. 61/744,936, entitled “Instrument for Soft TissueDissection,” filed on Oct. 6, 2012; and U.S. Provisional PatentApplication No. 61/783,834, entitled “Instruments, Devices, and RelatedMethods for Soft Tissue Dissection,” filed on Mar. 14, 2013, all ofwhich are incorporated herein by reference in their entireties.

BACKGROUND

Field of the Disclosure

The field of the disclosure relates to methods or devices used todissect tissue during surgery or other medical procedures.

Technical Background

Surgeons frequently are required to sever or separate tissues during asurgical procedure. Two techniques are commonly used: (1) “sharpdissection” in which the surgeon uses a cutting instrument to slice atissue, cutting with either scissors, a scalpel, electrosurgery, orother slicing instrument and (2) blunt dissection.

The advantage of sharp dissection is that the cutting instrument easilycuts through any tissue. The cut itself is indiscriminate, slicingthrough any and all tissues to which the instrument is applied. This isalso the disadvantage of sharp dissection, especially when trying toisolate a first tissue without damaging it, when the first tissue isembedded in and obscured by a second tissue or, more commonly, in manytissues. Accidental cutting of a blood vessel, a nerve, or of the bowel,for example, is not an uncommon occurrence for even the most experiencedsurgeons and can lead to serious, even life-threatening, intra-operativecomplications and can have prolonged consequences for the patient.

Isolation of a first tissue that is embedded in other tissues is thusfrequently performed by blunt dissection. In blunt dissection, a bluntinstrument is used to force through a tissue, to force apart twotissues, or to otherwise separate tissues by tearing rather thancutting. Almost all surgeries require blunt dissection of tissues toexpose target structures, such as blood vessels to be ligated or nervebundles to be avoided. Examples in thoracic surgery include isolation ofblood vessels during hilar dissection for lobectomy and exposure oflymph nodes.

Blunt dissection includes a range of maneuvers, including various waysto tear soft tissues, such as the insertion of blunt probes orinstruments, inverted action (i.e., spreading) of forceps, and pullingof tissues with forceps or by rubbing with a “swab dissector” (e.g.surgical gauze held in a forceps). When needed, sharp dissection is usedjudiciously to cut tissues that resist tearing during blunt dissection.

The general goal is to tear or otherwise disrupt tissue, such asmembranes and mesenteries, away from the target structure withouttearing or disrupting either the target structure or critical structuressuch as nearby vessels or nerves. The surgeon capitalizes on thedifferent mechanical behaviors of tissues, such as the differentstiffness of adjacent tissues or the existence of planes of softertissue between firmer tissues. Frequently, the goal is to isolate atarget tissue that is mechanically firm, being composed of more tightlypacked fibrous components, and is embedded in a tissue that ismechanically soft, being composed of more loosely packed fibrouscomponents (for example, loose networks of collagen, reticulin, andelastin). More tightly packed fibrous tissues include tissues composedof tightly packed collagen and other fibrous connective tissues, usuallyhaving highly organized anisotropic distributions of fibrous components,often with hierarchical composition. Examples include blood vessels,nerve sheaths, muscles, fascia, bladders, and tendons. More looselypacked fibrous tissues have a much lower number of fibers per unitvolume or are composed of less well organized materials such as fat andmesenteries. Fibrous components include fibers, fibrils, filaments, andother filamentous components. When a tissue is referred to as “fibrous”,the reference is typically to extracellular filamentous components, suchas collagen and elastin—proteins that polymerize into linear structuresof varying and diverse complexity to form the extracellular matrix. Asmentioned in the previous paragraph, the density, orientation, andorganization of fibrous components greatly determine the tissue'smechanical behavior. Sometimes, tissues are referred to as “tough,fibrous tissues” indicating that the fibrous or filamentous componentsare densely packed and comprise a significant fraction of the bulk ofthe tissue. However, all tissues are fibrous, to one extent or another,with fibers and other filamentous extracellular components being presentin virtually every tissue.

What is important to the present discussion is that softer tissues tearmore easily than firmer tissues, so blunt dissection attempts to proceedby exerting sufficient force to tear softer tissue but not firmertissue.

Blunt dissection can be difficult and is often time-consuming. Judgingthe force to tear a soft tissue, but not a closely apposed firm tissueis not easy. Thus, blood vessels can be torn. Nerves can be stretched ortorn. In response, surgeons attempt judicious sharp dissection, butblood vessels and nerves can be cut, especially a smaller side branch.This all leads to long, tedious dissections and increased risk ofcomplications, like bleeding, air leaks from the lungs, and nervedamage.

Surgeons frequently use forceps for blunt dissection. FIGS. 1A and 1Bshow a typical forceps 10 of the prior art. FIG. 1A shows the forceps 10in the closed position for clamping a tissue 34 between the opposingfirst clamp element 30 and second clamp element 31. FIG. 1B shows theforceps 10 in the open position, forcing tissue 34 apart. A first fingerengager 20 and an opposing second finger engager 21 are used to actuatethe mechanism. First finger engager 20 drives first clamp element 30,and second finger engager 21 drives second clamp element 31. A pivot 40attaches the first clamp element 30 and the second clamp element 31,permitting a scissor-like action to force the first clamp element 30 andthe second clamp element 31 together or apart, thereby clamping tissue34 between the two clamp surfaces 35 and 36 or rending tissue 34 by thespreading of the first clamp element 30 and the second clamp element 31.Frequently, a ratcheting clasp 50 is used to lock the first clampelement 30 and the second clamp element 31 together.

Laparoscopic and thoracoscopic (collectively referred here as“endoscopic”) instruments use a similar action. FIG. 2 shows an exampleof an endoscopic forceps 110 of the prior art. A first finger engager120 and an opposing second finger engager 121 are used to actuate themechanism. First finger engager 120 is rigidly mounted to the instrumentbody 150. Second finger engager 121 drives opposing clamp elements 130and 131. A pivot 140 attaches the two clamp elements 130 and 131, suchthat actuation of second finger engager 121 forces clamp elements 130and 131 together, thereby clamping a tissue between two clamp surfaces135 and 136. As in FIG. 1, endoscopic forceps 110 can be used to force atissue apart. Clamp elements 130 and 131 are closed, inserted into atissue, and then opened to tear the tissue.

For either instrument, forceps 10 or endoscopic forceps 110, a surgeonperforms blunt dissection by closing the forceps, pushing the closedforceps into a tissue and then, optionally, opening the forceps insidethe tissue, using the force applied by opening of the jaws of theforceps to tear the tissue apart. A surgeon thus proceeds to dissect atissue by a combination of pushing into the tissue and opening the jawsof the forceps.

Blunt dissection is commonly used for wet and slick tissues, and thesmooth, passive surfaces of most surgical instruments slide easily alongthe tissue, impairing the instrument's ability to gain purchase andseparate the tissue. Furthermore, the surgeon has only limited control,being able only to jab, move sideways, or separate. An improvedinstrument for blunt dissection that could differentially separate softtissues while not disrupting firm tissues would greatly facilitate manysurgeries.

SUMMARY OF THE DETAILED DESCRIPTION

Embodiments disclosed include methods and devices for blunt dissection,which differentially disrupt a patient's soft tissues while notdisrupting that patient's firm tissues. In one embodiment, adifferential dissecting instrument for differentially dissecting complextissue is disclosed. The differential dissecting instrument comprises ahandle, a central longitudinal axis, and an elongate member having aproximal end and a distal end. The differential dissecting instrumentalso comprises a differential dissecting member configured to berotatably attached to the distal end, the differential dissecting membercomprising at least one tissue engaging surface, a first torque-point,the first torque-point disposed to a first side of the axis of rotationof the differential dissecting member, and a mechanism, configured tomechanically rotate the differential dissecting member around the axisof rotation thereby causing the at least one tissue engaging surface tomove in at least one direction against the complex tissue. The mechanismcomprises at least one force-transmitting member possessing a distal endand a proximal end, the distal end being attached to the firsttorque-point member. The proximal end of the at least oneforce-transmitting member is attached to a motive source configured tooscillate the differential dissecting member. Further, the at least onetissue engaging surface is configured to selectively engage the complextissue such that when the differential dissecting member is pressed bythe surgeon into the patient's complex tissue, the at least one tissueengaging surface moves across the complex tissue and the at least onetissue engaging surface disrupts at least one soft tissue in the complextissue, but does not disrupt firm tissue in the complex tissue.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B show examples of the prior art. FIG. 1A shows forcepsused to grasp tissue;

FIG. 1B shows exemplary forceps used in blunt dissection to dividetissue;

FIG. 2 shows laparoscopic forceps of the prior art;

FIG. 3A through 3F show an exemplary differential dissecting instrument.FIGS. 3A through 3C show a differential dissecting instrument having arotating differential dissecting member within a shroud. FIG. 3D-1through 3D-3 show front and side views of a differential dissectingmember; FIG. 3D-1 is a side view of a differential dissecting member,while FIG. 3D-2 depicts a close-up of the surface of the differentialdissecting member, and FIG. 3D-3 shows a front view of that samedifferential dissecting member. FIG. 3E-1 through FIG. 3E-4 show fourdifferent types of differential dissecting members, differentialdissecting member type I, type II, type III, and type IV, respectively.FIG. 3F-1 and FIG. 3F-2 show a differential dissecting member in frontand side view, respectively, including a tissue to be dissected;

FIGS. 4A through 4F show how an exemplary differential dissectinginstrument disrupts soft tissue, but not firm tissue, in a complextissue, exposing the firm tissue. FIGS. 4D through 4F illustrate how adifferential dissecting member engages and disrupts tissues havingdispersed fibrous components but is unable to engage, and thus disrupt,fibrous components;

FIGS. 5A through 5C show the tissue engaging end of different exemplarydifferential dissecting instruments comprising a dissecting wheelmounted in a shroud. FIGS. 5A through 5B show an instrument with oneconfiguration of a dissecting wheel and FIG. 5C-1 and FIG. 5C-2 showanother instrument with a different configuration of a dissecting wheel;FIG. 5C-1 depict the dissecting wheel in exploded view away from theinstrument, while FIG. 5C-2 shows the dissecting wheel in place;

FIGS. 6A through 6D show different configurations of an exemplarydifferential dissecting member in a differential dissecting instrumentshowing how the axis of rotation of the differential dissecting membercan have many different orientations with respect to the differentialdissecting instrument, including differential dissecting instrumentshaving flexible or articulating elongate members;

FIGS. 7A and 7B show an exemplary differential dissecting instrumentthat uses a dissecting wire instead of a dissecting wheel or otherdifferential dissecting member;

FIGS. 8A through 8C show an exemplary differential dissecting instrumentthat uses a flexible belt as a differential dissecting member;

FIGS. 9A through 9C show how a varying the exposure of the tissueengaging surface of a differential dissecting member changes thebehavior of a differential dissecting instrument, especially the rangeof angles of exposure of the tissue engaging surface;

FIGS. 10A through 10C show how a varying the exposure of the tissueengaging surface of a differential dissecting member changes thedirections of the friction forces on a tissue and thus the angles ofstrain on that tissue;

FIGS. 11A and 11B show an exemplary differential dissecting instrumentwith water outlets that emit beside the differential dissecting member;

FIG. 12 shows an exemplary differential dissecting instrument having twoopposing flexible belts that generate opposing frictional forces andthus reducing torque on the differential dissecting instrument;

FIG. 13 shows an exemplary differential dissecting instrument can havemultiple components placed into the shroud, including suction lines,water tubes, and light emitting diodes;

FIG. 14-1 through FIG. 14-3 show how the elongate member of an exemplarydifferential dissecting instrument can be articulated with a bendableregion to facilitate placement of the differential dissecting member;FIG. 14-1 depicts the elongate member of the differential dissectinginstrument in Position 1, straight, FIG. 14-2 shows the elongate memberof the differential dissecting instrument bent at 45 degrees, and FIG.14-3 illustrates the elongate member of the differential dissectinginstrument bent at 90 degrees;

FIGS. 15A through 15E show different exemplary differential dissectingmembers illustrating several important dimensions and features ofdifferential dissecting members; FIG. 15A shows a top view of anexemplary differential dissecting member that rotates about a rotationaljoint; further, FIG. 15B-1 through 15B-3 depict a differentialdissecting member as in FIG. 15A; FIG. 15B-1 shows the differentialdissecting member in side view cross-section, FIG. 15B-2 depicts aclose-up view of the tip of the differential dissecting member shown inFIG. 15B-1, and FIG. 15B-3 shows a close-up view of the surface of thedifferential dissecting member shown in FIG. 15B-2; FIG. 15C illustratesanother embodiment of a differential dissecting member having ascalloped tissue engaging surface; FIG. 15D shows an oblique view of thedifferential dissecting member depicted in FIG. 15C; FIG. 15E-1illustrates an end-on view of the differential dissecting memberdepicted in FIG. 15C, FIG. 15E-2 depicts a close-up view of thetissue-engaging surface of the differential dissecting member shown inFIG. 15E-1, and FIG. 15E-3 details a very close-up view of the surfacefeatures of the differential dissecting member shown in FIG. 15E-1 andFIG. 15E-2;

FIG. 16-1 through FIG. 16-3 show one exemplary means for changing thelevel of aggressiveness of a differential dissecting member; FIG. 16-1shows a differential dissecting member with some pointed, butstill-not-sharp features, FIG. 16-2 shows a differential dissectingmember with more rounded features than shown in FIG. 16-1, and FIG. 16-3shows a differential dissecting member with even more blunt featuresthan those differential dissecting members shown in FIG. 16-1 or FIG.16-2;

FIG. 17A, FIGS. 17B-1, and 17B-2 show how features, such as scalloping,of the tissue engaging surface result in the tissue engaging surfacehaving varying angles of attack as it moves over a tissue; FIG. 17Adepicts a differential dissecting member with a lobate form, FIG. 17B-1shows that same differential dissecting member impinging on a tissue,and FIG. 17B-2 is a close-up view of the lobes of the lobatedifferential dissecting member detailing the angles of attack of thetissue engaging surface with respect to the tissue;

FIG. 18 shows how relative placements of the center of rotation and thecenter of gravity of an oscillating differential dissecting member cancause a differential dissecting instrument to vibrate;

FIGS. 19A through 19D show how an exemplary differential dissectingmember, or a shroud surrounding it, strain a tissue in the directionperpendicular to the direction of motion of the tissue engaging surface.FIG. 19D illustrates how this strain can align fibrous components insidethe tissue, thereby facilitating their disruption by the tissue engagingsurface;

FIG. 20 further illustrates how an exemplary differential dissectingmember disrupts tissue, including how the differential dissecting memberstrains the tissue and disrupts fibrous components, such as interstitialfibers;

FIGS. 21A through 21C-4 show how relative movement of the shroud and thedifferential dissecting member of a differential dissecting instrumentvary the wedge angle and thus can produce more or less strain in atissue; FIG. 21A shows a side view of a differential dissecting memberthat has a thin dissecting wheel and is wrapped in a shroud; FIG. 21B-1and FIG. 21B-2 further illustrate a front view of the shroudeddifferential dissecting member in FIG. 21A and a close-up view of same,respectively; FIG. 21C-1 through FIG. 21C-4 show four differentpositions of a shroud covering the differential dissecting member of thedifferential dissecting instrument;

FIG. 22 shows one example of an exemplary reciprocating mechanism for adifferential dissecting member that uses a scotch yoke mechanism toconvert rotation of a shaft to reciprocal oscillation of a differentialdissecting member;

FIGS. 23A through 23C further illustrate the scotch yoke mechanism shownin FIG. 22;

FIGS. 24A and 24B further illustrate the scotch yoke mechanism shown inFIG. 22;

FIGS. 25A through 24D further illustrate the scotch yoke mechanism shownin FIG. 22, including how more of the differential dissecting member canbe shrouded to reduce trauma to a patient's tissues;

FIG. 26A-1, FIG. 26A-2, FIGS. 26B-1, and 26B-2 show how an exemplarydifferential dissecting member can be fitted with retractable blade topermit a differential dissecting instrument to also perform sharpdissection of tissues; FIG. 26A-1 and FIG. 26B-1 show side views whileFIG. 26A-2 and FIG. 26B-2 show top views; FIG. 26A-1 and FIG. 26A-2 showthe differential dissecting member with a retractable scalpel withdrawn,while FIG. 26B-1 and FIG. 26B-2 show the same differential dissectingmember with the retractable scalpel extended;

FIGS. 27A and 27B show how an exemplary differential dissecting membercan be fitted with a clasping member to permit a differential dissectinginstrument to act as forceps;

FIG. 28 shows an exemplary differential dissecting member having atissue engaging surface and a lateral surface;

FIGS. 29A through 29E-2 show magnified views of the tissue engagingsurface and lateral surfaces of the differential dissecting member inFIG. 28 with the tissue engaging surface being comprised of analternating series of valleys and projections; FIG. 29C-2 depicts aclose-up of the corner of a projection shown in FIG. 29C-1; FIG. 29E-1and FIG. 29E-2 show two alternative versions of arrangements of valleysand projections forming the surface of a differential dissecting member;

FIGS. 30A through 30D show how the lateral surface of the differentialdissecting member in FIGS. 28 and 29A through 29C align and straintissues, including interstitial fibrous components and how straining ofthe interstitial fibrous components facilitates their alignment andentering a valley and then being torn by a projection;

FIG. 31 further illustrates from a different view how fibrous componentsof a tissue enter a valley and are then strained and torn by aprojection;

FIG. 32 shows an exploded view of a complete exemplary differentialdissecting instrument;

FIGS. 33A through 33C show an enlarged view of the differentialdissecting member of the differential dissecting instrument in FIG. 32,with emphasis on how a scotch yoke mechanism permits a rotating shaft todrive the reciprocal oscillations of the differential dissecting member;

FIG. 34 shows an exploded view of another exemplary differentialdissecting instrument having a retractable blade;

FIGS. 35A through 35C-2 show an enlarged view of the differentialdissecting member of the differential dissecting instrument in FIG. 34,including how this mechanism can also be used to vary the amplitude ofoscillation of the differential dissecting member; FIG. 35A shows anexploded view of an exemplary Differential Dissecting Instrument; FIG.35B depicts the details of assembly of an exemplary differentialdissecting member; FIG. 35C-1 and FIG. 35C-2 depict how the angularamplitude of a differential dissecting member can be controlled via thelongitudinal position of the cam receiver body;

FIGS. 36A-1, 36A-2, 36B-1, 36B-2, 36B-3, and 36B-4 show an exemplaryretractable blade that is a retractable hook having a more aggressivetissue engaging surface plus a hook with a sharpened elbow permittingselective slicing of tissue for sharp dissection; FIG. 36A-1 depicts thehook extended from the differential dissecting member, FIG. 36A-2 showsit retracted into the differential dissecting member; FIGS. 36B-1 and36B-2 show the hook extended, and FIGS. 36B-3 and 36B-4 show the hookretracted; FIG. 36B-1 and FIG. 36B-3 depict the differential dissectingmember in static position, while FIG. 36B-2 and FIG. 36B-4 show thedifferential dissecting member actively oscillating;

FIGS. 37-1, 37-2, 37-3, and 37-4 illustrate how the retractable hookshown in FIGS. 36A and 36B can be used to quickly and safely divide amembranous structure, like the peritoneum; FIG. 37-1 shows the hookextended from the tip of a static differential dissecting member whilethe differential dissecting instrument is suspended by the surgeon abovea patient's tissue, FIG. 37-2 depicts the hook extended from theoscillating differential dissecting member and so oscillating againstthe surface of the tissue, FIG. 37-3 shows the static differentialdissecting member with extended hook engaging the edge of a tissuecapsule, and FIG. 37-4 depicts the differential dissecting memberoscillating with extended hook, so cutting the tissue capsule layer;

FIG. 38 shows a complete exemplary differential dissecting instrumenthaving a pistol grip and the ability to rotate the instrument insertiontube and, thus, turn the plane of oscillation of the differentialdissecting member;

FIG. 39 shows how an exemplary differential dissecting instrument can befitted to the arm of a surgical robot and can, optionally, be fittedwith an electrically conducting patch for electrocautery;

FIGS. 40-1 and 40-2 show an exemplary laparoscopic version of adifferential dissecting instrument having electromechanical actuatorsdistal to an articulation, and in the straight and bent positions,respectively;

FIG. 41 shows one exemplary version of a differential dissectinginstrument driven by a flexible drive shaft;

FIGS. 42A through 42E show an oblique view and expanded views of oneembodiment of a differential dissecting instrument in slender pencilgrip form designed especially for open surgery;

FIGS. 43A through 43C show different embodiments of some mechanisms thatcan drive the oscillation of a differential dissecting member;

FIGS. 44A-1 through 44C-2 show different embodiments of mechanisms thatprotect both a differential dissecting instrument and a tissue beingdissected from excessive loading;

FIGS. 45A through 45G show a method for using a differential dissectinginstrument for separating a tissue plane without damaging blood vesselsand other anatomical structures in the tissue plane;

FIGS. 46A-1, 46A-2, 46B-1, 46B-2, 46C-1, and 46C-2 show an instrumentfor tunneling with a differential dissecting instrument coupled with anendoscope; and

FIGS. through 47D show another instrument for tunneling with adifferential dissecting instrument coupled with an endoscope andincluding accessory components to enhance dissection and to improve thefield of view for the endoscope.

DETAILED DESCRIPTION

Embodiments disclosed include methods and devices for blunt dissection,which differentially disrupt a patient's soft tissues while notdisrupting that patient's firm tissues. In one embodiment, adifferential dissecting instrument for differentially dissecting complextissue is disclosed. The differential dissecting instrument comprises ahandle, a central longitudinal axis, and an elongate member having aproximal end and a distal end. The differential dissecting instrumentalso comprises a differential dissecting member configured to berotatably attached to the distal end, the differential dissecting membercomprising at least one tissue engaging surface, a first torque-point,the first torque-point disposed to a first side of the axis of rotationof the differential dissecting member, and a mechanism, configured tomechanically rotate the differential dissecting member around the axisof rotation thereby causing the at least one tissue engaging surface tomove in at least one direction against the complex tissue. The mechanismcomprises at least one force-transmitting member possessing a distal endand a proximal end, the distal end being attached to the firsttorque-point member. The proximal end of the at least oneforce-transmitting member is attached to a motive source configured tooscillate the differential dissecting member. Further, the at least onetissue engaging surface is configured to selectively engage the complextissue such that when the differential dissecting member is pressed bythe surgeon into the patient's complex tissue, the at least one tissueengaging surface moves across the complex tissue and the at least onetissue engaging surface disrupts at least one soft tissue in the complextissue, but does not disrupt firm tissue in the complex tissue.

Specifically, “Differential Dissecting Instruments” are disclosed. Theterm “differential” is used because a Differential Dissecting Instrumentcan disrupt Soft Tissue while avoiding disruption of Firm Tissue. Theeffector end of a Differential Dissecting Instrument can be pressedagainst a tissue comprised of both Firm Tissue and Soft Tissue, and theSoft Tissue is disrupted far more readily than the Firm Tissue. Thus,when a Differential Dissecting Instrument is pressed into a ComplexTissue, the Differential Dissecting Instrument disrupts Soft Tissue,thereby exposing Firm Tissues. This differential action is automatic—afunction of the device's design. Far less attention is required of anoperator than traditional methods for blunt dissection, and risk ofaccidental damage to tissues is greatly reduced.

For the purposes of this application, “Soft Tissue” is defined as thevarious softer tissues separated, torn, removed, or otherwise typicallydisrupted during blunt dissection. “Target Tissue” is defined as thetissue to be isolated and its integrity preserved during bluntdissection, such as a blood vessel, gall bladder, urethra, or nervebundle. “Firm Tissue” is defined as tissue that is mechanicallystronger, usually including one or more layers of tightly packedcollagen or other extracellular fibrous matrices. Examples of FirmTissues include the walls of blood vessels, the sheaths of nerve fibers,fascia, tendons, ligaments, bladders, pericardium, and many others. A“Complex Tissue” is a tissue composed of both Soft Tissue and FirmTissue and can contain a Target Tissue.

FIGS. 3A, 3B, and 3C show the effector end of a Differential DissectingInstrument 300 that can differentially disrupt Soft Tissue while notdisrupting Firm Tissues. In this embodiment, a dissecting membercomprises a dissecting wheel 310 that rotates around shaft 320 that isheld inside cavity 331 inside shroud 330. FIG. 3A shows the separateparts. FIGS. 3B and 3C show two different views of the assembly. Thedissecting wheel 310 is turned by any of several mechanisms, such as amotor or a manually driven drive with appropriate means of transmission.Dissecting wheel 310 has tissue engaging surface 340 that can grab anddisrupt Soft Tissue but not Firm Tissue. Examples of tissue engagingsurface 340 and dissecting wheel 310 include a diamond grinding wheel oran abrasive stone or a surface otherwise covered by small obtrusions orprojections (further defined below) from the surface. Shroud 330obscures portions of dissecting wheel 310 such that only one portion ofdissecting wheel 310 is exposed. In use, dissecting wheel 310 rotates ata speed ranging from approximately sixty (60) to approximatelytwenty-five thousand (25,000) rpm or from approximately sixty (60) toapproximately one hundred thousand (100,000) rpm, with speed beingoperator selectable. Additionally, the direction of rotation ofdissecting wheel 310 can be reversed by the operator. Alternately,dissecting wheel 310 can oscillate (reciprocal oscillation) with afrequency ranging from about sixty 60 to approximately twenty thousand(20,000) cycles per minute in one embodiment. In another embodiment, thedissecting wheel 310 can oscillate (reciprocal oscillation) with afrequency ranging from about 2,000 to 1,000,000 cycles per minute.

Dissecting wheel 310 is one example of a “Differential DissectingMember” (hereinafter “DDM”) that can differentially disrupt Soft Tissuebut not Firm Tissue. FIG. 3D shows side, front, and oblique views of oneembodiment of a DDM 350 that has been separated from the rest of theDifferential Dissecting Instrument 300 for clarity. DDM 350 is comprisedof a body 360 having an axis of rotation 365 about which body 360rotates. Rotation can be oscillatory (i.e. back-and-forth) orcontinuous. Body 360 has an outer surface 361 with a tissue engagingsurface 370 distributed over at least a portion of the outer surface 361of body 360. Non-tissue engaging surface 371 is the portion of outersurface 361 not covered by tissue engaging surface 370. In thisembodiment, no portion of outer surface 361 that contacts a tissue, andespecially tissue engaging surface 370, should have features that aresufficiently sharp to slice tissue, so there should be no knife edges(like a scalpel or scissors), no sharply pointed teeth (like a saw), nosharp corners, and no sharp-edged fluting (like a drill bit or anarthroscopic shaver), where sharp means possessing a radius of curvatureless than 25 μm. Typical maximum dimensions of a DDM are betweenapproximately three (3) and approximately twenty (20) millimeters (mm).Alternatively, a small version for microsurgery can measure betweenapproximately two (2) and approximately five (5) mm.

The tissue engaging surface 370 is further comprised of a plurality ofprojections 375 (shown in expanded detail view of FIGS. 3D-1 through3D-3) from the outer surface 361 of body 360, each projection 375 havinga projection length 380 measured from trough to peak in a directionsubstantially perpendicular to that local region of outer surface 361 ofbody 360. Different projections 375 on tissue engaging surface 370 canall have the same projection length 380, or they can have differentprojection lengths 380. Projections 375 preferably have a projectionlength 380 less than approximately one (1) mm. Alternatively, for someembodiments the projection length can be greater than approximately one(1) mm but less than approximately five (5) mm. Collectively, allprojections 375 on a tissue engaging surface 370 have an averageprojection length (P_(avg)). Projections 375 are separated by gaps 385,preferably spanning a distance of approximately 0.1 mm to approximatelyten (10) mm.

Referring now to FIGS. 3D-1 through 3D-3, FIG. 3D-1 through 3D-3 showfront and side views of a differential dissecting member. FIG. 3D-1 is aside view of a differential dissecting member, while FIG. 3D-2 depicts aclose-up of the surface of the differential dissecting member, and FIG.3D-3 shows a front view of that same differential dissecting member.Body 360 of FIGS. 3D-1 through 3D-3 can optionally be shaped such thattissue engaging surface 370 is located at varying distances from theaxis of rotation 365. Thus, a placement radius R can be measured in aplane perpendicular to the axis of rotation 365 from the axis ofrotation 365 to any point on tissue engaging surface 370. There willthus be a minimum placement radius R_(min) having the shortest lengthand a maximum placement radius R_(max) having the longest length, and asshown in FIGS. 3D-1 through 3D-3 and 3E-1 through 3E-4, R_(min) isgreater than zero whenever the tissue engaging surface 370 does notcompletely cover the surface 361 of the DDM 350. Thus, if body 360 isshaped such that tissue engaging surface 370 is located at varyingdistances from the axis of rotation 365, then (R_(max)−Rmin) will begreater than zero. In some embodiments of a DDM, this relationship(R_(max)−R_(min)) is greater than approximately one (1) mm. In otherembodiments this relationship (R_(max)−R_(min)) is greater than P_(avg).Alternatively, as shown in the examples in FIG. 3D-1 through 3D-3 andFIG. 3E-1 through 3E-4, R_(min) is typically at least 5% shorter thanR_(max). Typical sizes for a DDM are R_(min)> approximately one (1) mmand R_(max)< approximately fifty (50) mm; however, smaller versions formicroscopic dissections can have smaller dimensions of R_(min)>approximately 0.5 mm and R_(max)< approximately five (5) mm.

Referring now to FIGS. 3E-1 through 3E-4, four different embodiments ofa DDM are shown in side view, with the axis of rotation 365 beingperpendicular to the plane of the page. The cross-sectional profile of aDDM in a plane perpendicular to the axis of rotation 365 is important,as will be discussed in subsequent paragraphs. Below are four scenariosfor a cross-sectional profile of a DDM.

-   -   DDM Type I: The cross-sectional profile can be any shape, except        circular or a wedge of a circle. The axis of rotation 365 is        located at any point within the cross-section as shown in FIG.        3D-1 through 3D-3 that yields the result that        P_(avg)<(R_(max)−R_(min)). As shown in FIG. 3D-1 through 3D-3, a        DDM Type I can include regular cross-sectional profiles and        irregular cross-sectional profiles, including various        asymmetries, wavy/undulating/scalloped borders, cut-outs,        involute borders, etc. In this example, the DDM Type I        reciprocally oscillates between two end positions (dotted        outlines). Alternatively, motion can be rotational.    -   DDM Type II: The cross-sectional profile is circular or the        wedge of a circle. The axis of rotation 365 is located at any        point within the cross-section such that it yields the result        that P_(avg)<(R_(max)−R_(min)) (i.e. the axis of rotation 365 is        not close to the center of the circle).    -   DDM Type III: The cross-sectional shape is circular or the wedge        of a circle. The axis of rotation 365 is located at any point        within the cross-section sufficiently close to the center of the        circle such that it yields the result that        P_(avg)˜(R_(max)−R_(min)) (i.e. the axis of rotation 365 is        approximately at the center of the circle).    -   DDM Type IV: The cross-sectional shape has a regularly repeating        feature on the perimeter, such as scalloping, that yields the        result that P_(avg)<(R_(max)−R_(min)) no matter where the axis        of rotation 365 is located, including at the centroid of the        cross-sectional shape. A Type I DDM and a Type IV DDM are        closely related in that the axis of rotation 365 can be anywhere        within the cross-sectional shape and still yield the result that        P_(avg)<(R_(max)−R_(min)).

The scallops, undulations, or any regularly repeating feature of a DDMdo not include perforations or holes in the tissue engaging surface 370for which the walls of the perforations do not significantly contacttissue. For example, the aspirating passages disclosed in U.S. Pat. No.6,423,078 comprise holes in the abrasive surface, which act as thetissue engaging surface, of an abrading member. These holes do notcomprise the features disclosed for DDMs because the holes act only asfluidic ports in the tissue engaging surface, and the walls of theaspirating passages are not brought to bear on tissue. Nevertheless,DDMs disclosed herein can include aspirating passages such as these.

DDMs of Type I through IV can also include any variety of shape out ofthe plane of the page. As stated earlier, “The cross-sectional profileof a DDM in a plane perpendicular to the axis of rotation 365 isimportant”. Thus, dissecting wheel 310 in FIG. 3A through FIG. 3C is anexample of a DDM Type III.

FIGS. 3F-1 and 3F-2 illustrates a DDM 390 that is similar to the DDM 350shown in FIGS. 3D-1 through 3D-3. DDM 390 has a first end and a secondend 392 wherein the first end 391 is directed away from the ComplexTissue 399 and is rotatably engaged with a mechanism (not shown) suchthat DDM 390 is rotated about an axis of rotation 365 by the mechanism.The mechanism can include motorized and manual drives. The second end392 is directed toward the Complex Tissue 399 and comprises asemi-ellipsoid shape defined by three orthogonal semi-axes: the majorsemi-axis A, the first minor semi-axis B, and the second minor semi-axisC, wherein major semi-axis A lies in the direction of a line connectingthe first end 391 and the second end 392; minor semi-axis C is parallelto the axis of rotation 365 (i.e. A is perpendicular to the axis ofrotation 365); and minor semi-axis B is perpendicular to both majorsemi-axis A and minor semi-axis C. The semi-ellipsoid can have a rangeof shapes (e.g., there may be different relationships between thelengths of the three semi-axes, including A=B=C, A≠B≠C, A>B and A>C). Inone embodiment, A>B>C has been found to be very effective for a DDM.

FIGS. 4A through 4C show how the effector end of Differential DissectingInstrument 300 can be used for dissection of a Complex Tissue, comprisedof both Soft Tissue and Firm Tissue, wherein the DDM is a dissectingwheel 310. In FIG. 4A, an operator initiates rotation of dissectingwheel 310, as indicated by arrow 410, before or upon contact with a SoftTissue 400. In FIG. 4B, the operator then presses the exposed tissueengaging surface 340 of dissecting wheel 310 into the volume of the SoftTissue 400 for blunt dissection to reach the Target Tissue 420 within.The arrows 430 and 440 in FIG. 4B show two possible operator-executedmotions of the Differential Dissecting Instrument 300. Only the portionof tissue engaging surface 340 of dissecting wheel 310 exposed outsideof shroud 330 contacts the Soft Tissue 400 and thereby disrupts thatportion of Soft Tissue 400 in contact with tissue engaging surface 340.Because the exposed, moving portion of tissue engaging surface 340 candisrupt tissue without further action by the surgeon (e.g. without thesurgeon's forcefully scrubbing a Differential Dissecting Instrument 300against Soft Tissue 400), tissue can be disrupted simply by applicationof the rotating dissecting surface 340 of dissecting wheel 310 to anypart of Soft Tissue 400; however, when dissecting wheel 310 contacts theFirm Tissue of Target Tissue 420, it does not disrupt the Target Tissue420. Note that pushing dissecting wheel 310 into Soft Tissue 400 asindicated by the arrowhead on arrow 430 is a “plunge”—the dissectingwheel 310 can be pushed blindly into Soft Tissue 400 because it will notdisrupt Firm Tissue and will, therefore, not disrupt Target Tissue 420.Other motions of Differential Dissecting Instrument 300 can be used todissect Soft Tissue 400, including motion orthogonal to arrows 430 and440, curvaceous motions, and other 3D motions. Once Target Tissue 420has been exposed, Differential Dissecting Instrument 300 can bewithdrawn, exposing the Target Tissue 420, as shown in FIG. 4C.

FIG. 4D through FIG. 4F show how one embodiment of a DDM disrupts SoftTissue but won't disrupt Firm Tissue. FIG. 4D depicts a sectional viewof a DDM as dissecting wheel 310 with tissue engaging surface 340 havingprojections 375. Dissecting wheel 310 moves in and out of the plane ofthe page, with shaft 320 (not shown) substantially parallel to the planeof the page. The projections 375 thus move through the plane of thepage. FIG. 4D further shows a volume of Soft Tissue 400 that remainssubstantially in place as dissecting wheel 310, tissue engaging surface340, and projections 375 travel through the plane of the page. Given themotion of the projections 375 relative to the roughly stationary SoftTissue 400, dissecting wheel 310 disrupts Soft Tissue 400. In detail,the Soft Tissue 400 is comprised of both fibrous components 401 andgel-like material 402. (Soft Tissues are frequently composed ofextracellular material with fibrous components 401, e.g. collagen fibersand small bundles of fibers, and with thin sheet components, e.g.thinner membranes, dispersed in water-swollen gel-like materials.)Projections 375 are capable of sweeping through gel-like material 402such that they encounter and then snag individual fibrous components 401(e.g. at points 450 and 451); fibrous components 401 are then torn bythe relative motion of projections 375 on the dissecting wheel 310through the plane of the page and Soft Tissue 400. As dissecting wheel310 is pushed deeper into tissue 400, projections 375 will snag deeperand deeper fibrous components, also tearing them. Thus, Soft Tissues 400with dispersed components can be dissected with a DDM.

FIG. 4E shows, in contrast to FIG. 4D, how a tightly packed fibroustissue can resist dissection by a dissecting wheel 310. Firm Tissues 403are frequently comprised of fibrous components 401 that are tightlypacked either into parallel, crossed, or other organized arrays (e.g.fascia and blood vessel walls), or into tightly packed 2D and 3D meshes,and a gel-like material 402 covers the arrays of fibrous components 401.In FIG. 4E, a Firm Tissue 403 is composed of a gel-like material 402(stippled region) thinly coating a layer of tightly packed fibrouscomponents 401, the filaments of which are depicted with their long axesperpendicular to the plane of the page, thus the cross-section of thefibrous components 401 is depicted as circular. In this image thedissecting wheel 310 reciprocally oscillates left-right on the page, asindicated by arrow 405, sweeping projections 375 over the surface ofFirm Tissue 403. Due to the tight packing of fibrous components 401 inthis Firm Tissue 403, projections 375 are unable to separately engageand snag fibrous components 401, and are thus unable to apply sufficientstress to tear fibrous components 401. Furthermore, gel-like material402 serves as a lubricant, causing projections 375 to tend to slip offof the tightly packed fibrous components 401 of Firm Tissue 403.Finally, any compliance of the surface of Firm Tissue 403 exposed todissecting wheel 310 will prevent developing tension in the Firm Tissue403 or fibrous components 401, resulting in the Firm Tissue 403deflecting away from any pressure exerted by dissecting wheel 310. FirmTissues 403 thus resist disruption by DDMs by a combination of tightpacking of fibrous and sheet components 401, lubrication of thesecomponents by gel-like materials 402, and compliance of the Firm Tissue403.

Motion of a DDM, as stated above, can be either rotational oroscillatory. The velocity of a point on a DDM past a specific region oftissue strongly influences the ability of a DDM to disrupt that tissue.FIG. 4F depicts a dissecting wheel 310 that sweeps left-right within theplane of the page (as shown by double headed arrow 460) over a SoftTissue 400 with a point of contact 470. The translational velocity ofpoint of contact 470 is determined by the rotational velocity of the DDMand the distance 480 separating point of contact 470 from the center ofrotation (not shown). For rotational motion, the translational velocityequals 2πDω, where D is the distance 480 and ω is the rotationalfrequency in rotations per second. For oscillatory motion, thetranslational velocity equals DΨ2X, where D is the distance 480, Ψ isthe oscillatory frequency in cycles per second, and X is the angle sweptin radians. For a differential dissector, distance 480 ranges from aboutone (1) mm to about forty (40) mm; rotational velocity ranges fromapproximately two (2) rotations per second to approximately threehundred fifty (350 rotations per second; oscillatory frequency rangesfrom about two (2) hertz (Hz) to about three hundred fifty (350) Hz; andangle swept ranges from 2° to 270°. Thus, the translational velocity ofpoint of contact 470 on a differential dissector can range from aboutone (1) mm per second to about sixty thousand (60,000) mm per second. Inone embodiment, a distance 480 of approximately fifteen (15) mm and anoscillatory motion with frequency of approximately one hundred (100) Hzsweeping through about forty-five degrees (45°), yielding abouttwenty-four hundred (2400) mm per second, is very effective for a numberof Soft Tissues. Note that this means that the velocities ofoperator-executed motions (as shown in FIG. 4) are always smaller thanthe velocity of a point of contact on a DDM during dissection becausesurgeons are careful during dissections, moving their instruments onlyslowly (usually much less than one hundred (100) mm per second).Additionally, motion of the DDM is described throughout this document asarising from a rotational motion (continuous rotation or reciprocal,i.e., back-and-forth, oscillation). However, any motion of a DDM,including rectilinear motion, relative to a tissue such that the tissueengaging surface of the DDM appropriately engages the tissue, asdescribed above, can be used.

A DDM can be forced against a blood vessel wall, the pleura, thepericardium, the esophagus, the gall bladder, and almost any other organor tissue comprised of or covered by a tightly packed fibrous tissue,and the DDM will not significantly disrupt such a Firm Tissue underlight hand pressure. Conversely, a DDM can be forced against a mesenteryor other Soft Tissue, and the Soft Tissue will rapidly disrupt underlight hand pressure. Differential dissectors fitted with any one of avariety of DDMs as disclosed herein have been found by the inventors torapidly dissect between the planes of lobes in the lung, to dissect aninterior mammary artery away from the inner wall of the chest, toseparate the blood vessels and bronchiole in the hilum of a lung lobe,to dissect the esophagus from surrounding tissues, to penetrate throughbulk muscle between, rather than through, the fiber bundles, to dissectfascia and tendons away from muscle fibers, to clean dissected fascia,to expose branched vascular and lymphatic structures, to dissect pocketsinto tissues and to separate tissue planes in many different tissues.The utility of a differential dissector is broad and, thus, has manypotential uses. Importantly, due to the composition of skin and ofsurgical gloves, the skin or surgical gloves are not cut or otherwisedisrupted by a DDM, even when significant pressure is applied. Theinventors have shown that an oscillating DDM of the type disclosedherein can be held against a cheek of the face without any harm. Thus, adifferential dissector is inherently safe to use, which simplifies useduring surgery, especially when the surgeon's fingers must be near thepoint of dissection.

DDMs are preferably formed from a rigid material, such as a metal or arigid polymer (e.g., Shore A equal to or greater than 70), rather thanfrom softer polymers and elastomers (e.g. Shore A less than 70). Use ofa rigid material keeps the projections from the tissue engaging surfacefrom deflecting away from the tissue, as might occur if a softermaterial was used. DDMs or their component portions can be machined frombulk material, constructed via stereolithography, molded by any of themeans well known in the art (e.g. injection molding), or by any suchmethod known in the art.

The projections of a tissue engaging surface of a DDM can be fabricatedby any of several means. Projections can be formed by coating the tissueengaging surface with grit similar to sandpaper using grit coarser than1000 but finer than 10 on the Coated Abrasive Manufacturers Institutestandard. Grit can include particles composed of diamond, carborundum,metal, glass, sand or other materials known in the art. Projections canbe formed into the surface of the material composing a DDM by sanding,sandblasting, machining, chemical treatment, electrical dischargemachining, or other methods known in the art. Projections can be moldeddirectly into the surface of a DDM. Projections can be formed onto thesurface by stereolithography. Projections can be irregularly shaped,like particles of grit, or they can be regularly shaped having definedfaceted, curved, or sloped surfaces. The projections may be elongate,and the long axis of these projections may have an angle with respect tothe tissue engaging surface. Projections possess a cross-sectional shapewhen viewing the tissue engaging surface from above, and this shape maybe round, faceted, or complex. The cross-sectional shapes of projectionsmay be oriented with respect to the direction of travel of the DDM.

Keeping the tissue wet helps differential dissection. A well-wetted FirmTissue is better lubricated, greatly reducing disruption by a DDM.Conversely, a well-wetted Soft Tissue remains water-swollen and soft,separating the spacing of individual fibers, facilitating their beingengaged and torn by the projections from the tissue engaging surface ofa DDM. Wetting of the tissue can be accomplished by any of severalmeans, including simply irrigating the tissue with physiological salineduring dissection. Irrigation can be performed with procedures alreadyused in surgery, such as an irrigation line, or by one of the devicesdisclosed below. Additionally, wetting of the tissue, and thus also thetissue engaging surface of the DDM, reduces clogging of the tissueengaging surface with disrupted tissue.

FIG. 5A and FIG. 5B show another embodiment of the effector end of aDifferential Dissecting Instrument 500 which has a DDM Type IIIconfigured as a circular cylinder 510. FIG. 5A shows circular cylinder510, with shaft 520 separate from the shroud 530. The tissue engagingsurface 540 covers the side of circular cylinder 510. The two-headedarrow indicates rotation about the axis of rotation 575. FIG. 5B showsboth parts configured for use with only a limited portion of tissueengaging surface 540 exposed.

FIGS. 5C-1 and 5C-2 show another embodiment of the effector end of aDifferential Dissecting Instrument with a different configuration forthe shroud and DDM, here another DDM Type III. FIGS. 5C-1 and 5C-2 showa Differential Dissecting Instrument 550 with a dissecting wheel 560,with shaft 570 separate from the shroud 580. Tissue engaging surface 590covers the periphery of dissecting wheel 560. The two-headed arrowindicates the axis of rotation 575. FIG. 5C-2 shows both partsconfigured for use with only a limited portion of tissue engagingsurface 590 exposed. This configuration is problematic because shroud580 makes it difficult to position the tissue engaging surface 590against a tissue, and shroud 580 blocks the operator's view.

FIG. 6A shows one embodiment of a Differential Dissecting Instrument 600that includes a handle 610 for an operator. Handle 610 connects toelongate member 620 comprising a first end 621 connected to handle 610and a second end 622 connected to a DDM 630. Elongate member 620 can beshorter, allowing better manual control of the DDM 630 on an instrumentfor open surgery, or it can be longer, allowing Differential DissectingInstrument 600 to be a laparoscopic instrument. The drive mechanisms forrotating DDM 630, such as a rotating drive shaft for a Scotch yoke or acrank/slider, are readily adapted to any elongate member 620, long orshort, or to any device capable of driving DDM 630. DDM 630 is a TypeIII DDM rotatably mounted to elongate member 620 at second end 622 suchthat DDM 630 reciprocally oscillates about its axis of rotation 640, asindicated by the double-headed arrow (Axis of rotation 640 isperpendicular to the plane of the page in FIG. 6A). First end 621 andsecond end 622 define a centerline 650 of elongate member 620. Thetangent 651 of centerline 650, as centerline 650 approaches second point622, and axis of rotation 640 thus define a presentation angle 670 (notshown—perpendicular to page). In this example, the presentation angle670 is 90° (i.e., axis of rotation 640 is aligned perpendicular totangent 651). Rather than a handle 610, first end 621 of elongate member620 can attach to the arm of a robot for robotic surgery. A DDM caneasily be adapted to any other device capable of moving or rotating theDDM.

FIG. 6B shows another embodiment of a similar Differential DissectingInstrument 601 but with the axis of rotation parallel to the centerline.Handle 610 connects to elongate member 620 comprising a first end 621connected to the handle 610 and a second end 622 connected to a Type IIIDDM 631. DDM 631 is rotatably mounted to elongate member 620 at secondend 622 such that DDM 631 reciprocally oscillates about its axis ofrotation 640. The axis of rotation 640 is parallel to the plane of thepage in FIG. 6B. First end 621 and second end 622 define a centerline650 of elongate member 620 with tangent 651 as centerline 650 approachessecond end 622. Axis of rotation 640 is thus aligned parallel to tangent651 (i.e., the presentation angle 670 is 0°). (Again, presentation angle670 is not presented in FIG. 6B because presentation angle is 0°.)Differential Dissecting Instrument 601 is thus similar to DifferentialDissecting Instrument 550 in FIG. 5C and thus has similar limitations,including that it is difficult to position the tissue engaging surfaceof DDM 631 against a tissue without blocking the operator's view.

FIG. 6C shows another embodiment of a Differential Dissecting Instrument603 having a curved elongate member 620 with curved centerline 650 andtangent 651 to centerline 650 as centerline 650 approaches second point622. The axis of rotation 640 is perpendicular to tangent 651 formingpresentation angle 670, which is 90° in this example. Elongate member620 may similarly be bent, jointed, articulated, or otherwise made of aplurality of parts. In all cases, the presentation angle 670 is formedby the axis of rotation of a DDM and the tangent of the centerline as itapproaches second point 622.

FIG. 6D shows another embodiment of a Differential Dissecting Instrument604 similar to Differential Dissecting Instrument 602 in FIG. 6B. Handle610 connects to elongate member 620 comprising a first end 621 connectedto the handle 610 and a second end 622 connected to a Type III DDM 631.DDM 631 is rotatably mounted to elongate member 620 at second end 622such that DDM 631 reciprocally oscillates about its axis of rotation640. The axis of rotation 640 is parallel to the plane of the page inFIG. 6D. First end 621 and second end 622 define a centerline 650 ofelongate member 620 with tangent 651 as centerline 650 approaches secondpoint 622. Axis of rotation 640 is thus aligned at a non-zero angle totangent 651 (i.e., the presentation angle 670 is between 0° and 90°). Inpreferred embodiments, presentation angle 670 does not equal 0°, for thereasons described for Differential Dissecting Instrument 603 in FIG. 5Cand FIG. 6B.

FIG. 7A and FIG. 7B show another embodiment of the effector end of aDifferential Dissecting Instrument 700 that uses a dissecting wire 710as the DDM. FIG. 7A shows the assembled device. Dissecting wire 710stands out a distance 725 from the backing surface 726 of a shroud 730,the dissecting wire 710 emitting from a first post 720, spanning gap722, and entering a second post 721 on the end of shroud 730. Dissectingwire 710 is a continuous loop of wire driven such that the exposedsection of dissecting wire 710 travels in the direction indicated byarrow 723 across gap 722 in FIG. 7A.

FIG. 7B shows a schematic side view of this embodiment of a DifferentialDissecting Instrument 700 that depicts the loop of dissecting wire 710and drive mechanism. Dissecting wire 710 is a continuous loop thatpasses over a first idler bearing 750 housed in first post 720 and thenemits from first post 720. Dissecting wire 710 travels across gap 722,moving in the direction of arrow 723, and enters second post 721 whereit passes over second idler bearing 751. The loop of dissecting wire 710travels further back in shroud 730 where it passes over a drive wheel760 which is turned by, for example, a motor in the direction of curvedarrow 724. Thus, rotation of drive wheel 760 drives dissecting wire 710.Note that dissecting wire 710 can be a flexible linear element with anycross-sectional shape, so instead of being a wire of circularcross-sectional shape, dissecting wire 710 could be a flexible flat beltwith the outward-facing side possessing a tissue engaging surface.Similarly, dissecting wire 710 can be a flexible cord having greaterdiameter than a wire would permit turning over idler bearings 750 and751; the flexible cord having a tissue engaging surface. Further, thedistance 725 between the dissecting wire 710 and the backing surface 726can be arbitrarily large or small, for example the distance 725 can belarge enough to create a substantial area encircled by the dissectingwire 710, the backing surface 726 and the first post 720 and the secondpost 721, thus able to surround a Target Tissue to be removed. Incontrast, distance 725 can be zero, where the dissecting wire 710 runsalong the surface of the shroud 730, or even in a slight accommodatinggroove that supports the dissecting wire 710 from behind. Such anaccommodating groove can have a semi-circular cross-sectional shape thusexposing just a portion of the cross-sectional shape of the dissectingwire 710 to the tissue to be dissected. Further, the shape of thebacking surface 726 can be flat, or it can be curved, subtly orpronounced, and the curved surface can possess convex areas, concaveareas, or a combination.

FIG. 8A-8C show the effector end of a Differential Dissecting Instrument800 that uses a flexible belt as the DDM. FIG. 8A shows the separateparts. Flexible belt 840 has an outer tissue engaging surface 850.Flexible belt 840 travels over idler wheel 810, which rotates aroundshaft 820, all of which are housed in shroud 830.

FIG. 8B shows the assembled effector end of Differential DissectingInstrument 800 with only a limited portion of tissue engaging surface850 of flexible belt 840 exposed.

FIG. 8C shows a top view of a schematic of one example of how a flexiblebelt, such as flexible belt 840, can be driven. Idler wheel 810 anddrive wheel 860 are mounted inside shroud 830. Flexible belt 840 wrapsaround idler wheel 810 and drive wheel 860. Drive wheel 860 is poweredto rotate such that flexible belt 840 is driven in the directionindicated by curved arrow 870. The tissue engaging surface 850 exposedoutside the shroud 830 is then used to disrupt tissue. The drive wheel860 can be driven by any of several mechanisms, such as a motor, handcrank, etc. The drive wheel 860 and the idler wheel 810 need not beright circular cylinders, nor must their rotational axes be parallel.

The extent of exposure of tissue engaging surfaces outside of theshrouding can be greater or less than those shown in the prior examples.In fact, varying the exposure changes several aspects of the behavior ofthe Differential Dissecting Instruments.

First, a larger exposure, increases the exposed area of the tissueengaging surface, which increases the amount of tissue disrupted perunit time and increases the surface area of tissue removed. Thus,decreasing the exposure allows more precise removal of tissue, but itreduces the total amount of material removed. Second, increasing theexposure changes the angle of exposed tissue engaging surface. ConsiderFIGS. 9A through 9C, which show top view schematics of the effector endof Differential Dissecting Instrument 800 with successively restrictedexposure of tissue engaging surface 850 as controlled by the aperture900 in the shroud. Aperture 900 is largest in FIG. 9A and smallest inFIG. 9C. As the exposure is restricted, the range of angles of thearrows normal to tissue engaging surface 850 decreases. In FIG. 9A, thetissue engaging surface 850 disrupts both forward and on the sides. InFIG. 9C, the tissue engaging surface 850 disrupts only forward. Thus,when the tissue engaging surface 850 is applied to a tissue, differentdirections of contact are applied, depending on the angle of the exposedtissue engaging surface.

Second, this increasing angle of exposure of the tissue engaging surface850 also changes both the angles at which the contacted surface of atissue is strained and the torque on the instrument. Consider FIGS.10A-10C which show the friction on a tissue 400 created by applicationof a tissue engaging surface 1010.

In FIG. 10A, tissue engaging surface 1010 is moving in the direction ofarrow 1020. This produces a friction force in the direction of arrow1030. The larger the area of contact, the larger the friction force. Thefriction force both pulls the tissue 400 sideways (in the direction ofarrow 1030), shearing the tissue 400, and forces the tissue engagingsurface 1010 in the direction opposite arrow 1020. If tissue engagingsurface 1010 is mounted on an instrument 1060 at a distance from thepoint 1040 held by an operator, then the friction force places a torque1050 about point 1040. This torque can cause the end 1070 opposite point1040 of instrument 1060 to be pulled away from the desired point ofapplication, making control of dissection more difficult. Thus, limitingthe extent of exposure of a tissue engaging surface reduces the frictionforce and improves control by reducing torque on the handle.

FIG. 10B shows how a circular tissue engaging surface 850 producesfriction forces normal to the tissue engaging surface 850 and thus, indifferent directions depending on the range of contact of the tissue 400on the circular tissue engaging surface 850. The resultingmultidirectional shearing forces on the tissue 400 produce more complexstrain patterns in the tissue 400. As in FIG. 10A, the friction forcestill produces a net upward force 1080 on the tip of shroud 830;however, it does not produce a net left/right (into and out of thetissue 400) force on the tip of shroud 830. FIG. 10C shows that reducingthe exposure of tissue engaging surface 850 by narrowing aperture 900makes the friction force on the tissue more 1-dimensional, simplifyingstrain patterns in the tissue.

Despite this discussion of friction against a tissue, as discussed abovewith respect to wetted tissues, a DDM as described herein has theunusual quality of being effective when it has low friction with respectto a Complex Tissue. The non-tissue engaging surface and the tissueengaging surface are effective even when the entire DDM is fully bathedwith a lubricant, such as a surgical lubricant or a hydrogel lubricant.

In surgery, it is preferable to minimize unintended transport of tissuesto other parts of the body. Disrupted pieces of tissue can adhere to thetissue engaging surfaces of the Differential Dissecting Instrumentsdisclosed here. Unintended transport can be minimized in two ways.First, narrowing and controlling the shape of the aperture 900 as shownin FIG. 10B and FIG. 10C means that fragments of disrupted tissueadhering to the tissue engaging surface 850 will only be transported ashort distance before being deposited on or entering the shroud.Similarly, if they attach to but are then thrown tangentially away fromthe tissue engaging surface 850 by inertia, then narrowing the aperture900 will reduce the surface area available for adhesion, the timeavailable for adhesion and the distance that material can beaccelerated. Second, the tissue engaging surface 850 can be maderesistant to tissue adhesion. Surface treatment of a tissue engagingsurface 850 can be achieved by any of several techniques known in theart, such as chemical treatment, vapor deposition, sputtering, andothers. For example, fluorinating the tissue engaging surface 850 by anyof several known methods (e.g. dip coating, chemical deposition,chemical cross-linking such as with silanes, etc.), can make the tissueengaging surface 850 resist tissue adhesion by both hydrophilicmaterials and carbon-based hydrophobic tissue components. In oneembodiment, diamond/carbide coated tissue engaging surfaces may be used,which we have discovered to be much less likely to have tissue adhere tothese surfaces.

Transport of materials can also be reduced by the use of an oscillating(reciprocating) motion of the DDM, rather than a continuousunidirectional or continuous rotational motion. Oscillation preventstransport over distances exceeding the distance of oscillation, whichcan be over only a few degrees of rotation (e.g. 5 degrees to 90degrees). Any of a number of mechanisms can be used to drivereciprocating oscillating motion with a rotating motor, such as a Scotchyoke or crank/slider.

Tissue adherence is also a problem for decreasing the effectiveness ofthe tissue engaging surface 850. Clogging of the tissue engaging surface850 creates a thick coat of material over the tissue engaging surface850, making it much less effective at ablating Soft Tissue. As above,making the surface resistant to adhesion by tissues decreases thisproblem. Fluorinated tissue engaging surfaces and diamond/carbide tissueengaging surfaces don't clog as readily, especially when disruptingfatty tissues.

Clogging is also reduced if the tissue is wet and further if the tissueengaging surface 850 is flushed with water, as discussed earlier. FIG.11A and FIG. 11B show a Differential Dissecting Instrument 1100 in whicha first array of 3 water outlets 1111 emits beside tissue engagingsurface 850 from shroud 830. A second array of 3 water outlets 1112emits on the opposite side of tissue engaging surface 850. Otherarrangements of water outlets are possible. FIG. 11A shows a solid modelin oblique view. FIG. 11B shows the top view for a schematic ofDifferential Dissecting Instrument 1100 in which water tube 1121 carrieswater, or other fluid such as physiological saline, inside and to oneside of shroud 830 to water outlets 1111, and a second water tube 1122carries fluid inside and to the other side of shroud 830 to wateroutlets 1112. Water outlets 1111 and 1112 emit from opposite sides ofaperture 900, providing fluid to both sides of tissue engaging surface850. The liquid emitting from water outlets can, optionally, carryphysiologically active materials, either dissolved or suspended in theliquid. Physiologically active materials can include variouspharmaceutical compounds (antibiotics, anti-inflammatories, etc.) andactive biomolecules (e.g. cytokines, collagenases, etc.)

Appropriate arrangement of tissue engaging surfaces 850 creates frictionforces on tissues that can be used to advantage during blunt dissection.FIG. 12 shows a Differential Dissecting Instrument 1200 having two,opposing flexible belts 1201 and 1202 exposed in aperture 1230. Eachbelt is configured as in FIG. 10B with flexible belt 1201 running overidle 1211 and flexible belt 1202 running over idle 1212, but theflexible belts 1201 and 1202 circulate in opposite sense with respect toeach other. Thus, the flexible belt 1201 and the flexible belt 1202 runside by side in the same direction as shown by arrows 1203 and 1204 butin opposite directions when exposed to the tissue 1205, as shown byarrows 1271 and 1272. Thus, the flexible belt 1201 creates a net force1251 downward and the flexible belt 1202 creates a net force 1252 upwardon shroud 1220, whereby these forces 1251 and 1252 cancel, leavinglittle or no net force on the shroud 1220. This eliminates any torquingof Differential Dissecting Instrument 1200 (as described in FIG. 10A),making it easier for an operator to control. Additionally, the opposingdirections of motion 1271 and 1272 of flexible belts 1201 and 1202create opposing frictional forces on tissue 1205 during dissection,thereby pulling the tissue 1205 apart in the region identified by doubleheaded arrow 1260. This pulling action can facilitate blunt dissectionby tearing the tissue in the region of double headed arrow 1260. Notethat the gap 1280 between flexible belts 1201 and 1202 inside shroud1220 can be varied and can be reduced to zero such that flexible belts1201 and 1202 are in contact. Contact between flexible belts 1201 and1202 can help a drive mechanism match the rates of travel of flexiblebelts 1201 and 1202. In fact, friction between flexible belts 1201 and1202 can allow one belt, for example 1201, to drive the other belt, inthis example 1202. Thus a motor, for example, can actively driveflexible belt 1201, and flexible belt 1202 is then driven by flexiblebelt 1201. This can simplify the drive mechanism for two belts.

FIG. 13 shows how the shroud 1330 of a Differential DissectingInstrument 1300 can house other items, permitting greater functionality.Dissecting wheel 810 is exposed at aperture 900. Suction lines 1301 and1302 can connect to the front of the shroud 1330 near tissue engagingsurface 850, helping to remove any debris from disruption or excessfluid, such as fluid from water tubes 1121 and 1122 which emit throughwater outlets 1111 and 1112. Light emitting diodes (LEDs) can be placedon shroud 1330 to better illuminate an area for blunt dissection; forexample, LEDs 1311 and 1312 are supplied with power by cables 1313 and1314, respectively, and light from LEDs 1311 and 1312 directlyilluminates the tissue in the region of disruption.

FIGS. 14-1 through 14-3 show how the elongate member 1410 of aDifferential Dissecting Instrument 1400 can be articulated with abendable region 1430 such that a user can achieve variable bending ofthe elongate member 1410 to facilitate placement of the DDM 1420. FIG.14-1 depicts the elongate member of the differential dissectinginstrument in Position 1, straight, FIG. 14-2 shows the elongate memberof the differential dissecting instrument bent at 45 degrees, and FIG.14-3 illustrates the elongate member of the differential dissectinginstrument bent at 90 degrees. In Position 1 (FIG. 14-1), the elongatemember 1410 is straight. In Position 2 (FIG. 14-2) and then in Position3 (FIG. 14-3), elongate member 1410 is successively bent at bendableregion 1430 such that the DDM 1420 moves from forward-facing in Position1 to side-facing in Position 3. Bendable region 1430 can be anarticulated joint or any other mechanism to permit bending.

FIGS. 15A-15E show different DDMs, illustrating several importantdimensions and features of DDMs. FIG. 15A shows a top view of anexemplary differential dissecting member that rotates about a rotationaljoint. FIG. 15A shows a top view of a DDM 1500 that rotates about arotational joint 1510. Actuation of DDM 1500 causes it to reciprocallyoscillate up and down, as shown by the double headed arrow 1506 suchthat tissue engaging surface 1520 (pebbled section) swings through anarc with radius R_(A). Oscillation of DDM 1500 can swing through a rangeof ±90 degrees. The tissue engaging surface has a minimum radius R_(S)in the plane of rotation (the plane perpendicular to the plane ofrotation—the plane of the page here).

FIG. 15B shows a side view in cross-section with two successivelyenlarged views. (DDM 1500 thus oscillates in and out of the page in thisview.) FIG. 15B-1 through 15B-3 depict a differential dissecting memberas in FIG. 15A; FIG. 15B-1 shows the differential dissecting member inside view cross-section, FIG. 15B-2 depicts a close-up view of the tipof the differential dissecting member shown in FIG. 15B-1, and FIG.15B-3 shows a close-up view of the surface of the differentialdissecting member shown in FIG. 15B-2. First side 1530 and tissueengaging surface 1520 join at first margin 1540, having a radius ofcurvature R_(E), and second side 1531 and tissue engaging surface 1520join at second margin 1541, having radius of curvature R_(E), where theradii of curvature of first margin 1540 and second margin 1541 can bedifferent, but should be large enough such that the first margin 1540and the second margin 1541 are not sharp. Tissue engaging surface 1520is then created by projections 1550 with a maximum length L_(max),defined as the maximum length of a feature from the innermost trough tothe outermost peak.

FIG. 15C illustrates a different DDM 1501 having a scalloped tissueengaging surface formed by surface features 1560. Here, the surfacefeature 1560 is a convex lobe, but a surface feature 1560 can be anyregular or repeating feature on the tissue engaging surface 1520 havinga minimum radius of curvature R_(S). Furthermore, surface features canhave a profile that is not in the plane of rotation, as shown in FIG.15D and FIG. 15E. FIG. 15D shows an oblique view and FIG. 15E shows anend-on view. FIG. 15E-1 illustrates an end-on view of the differentialdissecting member depicted in FIG. 15C, FIG. 15E-2 depicts a close-upview of the tissue-engaging surface of the differential dissectingmember shown in FIG. 15E-1, and FIG. 15E-3 details a very close-up viewof the surface features of the differential dissecting member shown inFIG. 15E-1 and FIG. 15E-2. The inserts in FIG. 15E-1 through 15E-3 showsuccessively magnified sections of the DDM 1502 taken along the 45°angle. DDM 1502 has surface features 1570 with a profile in a plane at45° to the plane of rotation. As with DDM 1501 in FIG. 15C, the tissueengaging surface 1520 of DDM 1502 has projections 1550 with a maximumlength L_(max). In one embodiment, R_(A) can be between approximatelyone (1) mm and approximately one hundred (100) mm. In one embodiment,R_(S) can be between approximately 0.1 mm and approximately ten (10) mm.In one embodiment, R_(E) can be between approximately 0.05 mm andapproximately ten (10) mm, such that no slicing edge is presented to atissue. Alternatively, for some embodiments of a DDM, Rs and Re can beas small as about 0.025 mm.

DDMs can have tissue engaging surfaces that are scalloped, or notched,or have undulating profiles such that the angle of attack of the tissueengaging surface with respect to the surface of the tissue varies as thetissue engaging surface passes over a given point in the tissue. Infact, the angle of attack varies for any DDM for whichP_(avg)<(R_(max)−R_(min)), e.g. for a DDM Type I, Type II, or Type IV. Avarying angle of attack makes the dissecting action more aggressive, inwhich a more aggressive DDM is better able to disrupt a firmer tissueand a less aggressive DDM is less able to disrupt that same tissue.

FIGS. 16-1 through 16-3 show an alternate means by which DDMs can bemade with different levels of aggressiveness, i.e. the aggressiveness ofa DDM can be designed. DDM 1600 rotates about an axis of rotation 1610and has a tissue engaging surface 1620 bearing projections 1622. Theseprojections (FIG. 16-1) have more pointed tips (but still not sharpenough to slice). DDM 1640 has a tissue engaging surface 1650 bearingprojections having more rounded tips 1652 (FIG. 16-2). DDM 1680 has atissue engaging surface 1690 bearing projections with even more roundedtips 1692 (FIG. 16-3). DDM 1600 is more aggressive than DDM 1640 whichis more aggressive than DDM 1680.

FIG. 17A shows one embodiment of a DDM 1700 having a scalloped tissueengaging surface 1710 and a center of rotation 1720. DDM 1700 is thus anexample of a DDM Type IV. Oscillation of DDM 1700 back and forth asshown by double headed arrow 1730 causes tissue engaging surface 1710 tomove over a tissue such that the edges of the scallop bring the tissueengaging surface 1710 to bear at different angles of attack as eachscallop passes over the tissue.

FIGS. 17B-1 and 17B-2 illustrate the action of DDM 1700 against a tissue1750. FIG. 17B-1 shows that same differential dissecting memberimpinging on a tissue, and FIG. 17B-2 is a close-up view of the lobes ofthe lobate differential dissecting member detailing the angles of attackof the tissue engaging surface with respect to the tissue. The angle ofattack (the angle θ between the direction of motion and the tangent tothe tissue engaging surface 1710 at a point of contact) is shown at twopoints P₁ and P₂ on the tissue engaging surface 1710. θ₁ is smaller thanθ₂. Similar action can be achieved with a DDM 1800, as shown in FIG. 18,by using a circular tissue engaging component 1805 with tissue engagingsurface 1810 and a center of rotation 1820 that is not the center ofcircular tissue engaging component 1805 (e.g., a DDM Type II).Oscillation of tissue engaging component 1805 back and forth as shown bydouble headed arrow 1830 causes tissue engaging surface 1810 to moveover a tissue such that the tissue engaging surface 1810 moves such thatthe angle of attack varies at each point on the tissue engaging surface1810 on the perimeter of the circular tissue engaging component 1805.

FIG. 18 illustrates another important point, especially for acceleratingmotions of a DDM against a tissue 1850, and accelerations occur whenevera DDM is loaded or unloaded and whenever an oscillating DDM deceleratesafter sweeping one direction and accelerates to sweep in the oppositedirection. DDM 1800 is mounted with its center of gravity 1870 displacedfrom the center of rotation 1820. The solid double-headed arrow 1830shows the rotation about the center of rotation 1820, and the dasheddouble-headed arrow 1840 shows the motion of center of gravity 1870. Theforce of accelerating the mass of DDM 1800 and the distance between thecenter of gravity 1870 and the center of rotation 1820 create a momentabout the center of rotation 1820 which causes a differential dissectorto vibrate. This moment will cause the handle of a differentialdissector, to which the DDM 1800 is attached, to shake. DDMs composed ofdenser materials will make the shaking more extreme. It can, thus, beadvantageous to make DDMs from less dense materials, like rigid polymersrather than metals, to decrease shaking of the handle. Conversely, onemight arrange a countering moment through appropriate distribution ofmass within a DDM to place the center of gravity at the axis ofrotation.

The entirety of the surface of a DDM can be tissue engaging.Alternatively, selected portions of the surface can be tissue engaging.This can be advantageous to restrict dissection effects to one region ofthe surface of the DDM, the forward-looking surface, for example. FIG.19A through FIG. 19D show a Differential Dissecting Instrument 1900 thathas a DDM that is a dissecting wheel 1910 that is similar to that shownin FIG. 3A through FIG. 3C; however, the tissue engaging surface isrestricted to a thin tissue engaging strip 1920 around the outerperimeter of dissecting wheel 1910 which rotates around axis of rotation365. The remainder comprises the non-tissue engaging surface 1930,disposed laterally to either side of tissue engaging strip 1920, of theexposed surface of the dissecting wheel 1910 and has a much smoothersurface, optionally being glass smooth, free of projections, orotherwise unable to engage fibers in the tissues. FIG. 19B illustrateshow a dissecting wheel 1910 fits into shroud 1940 and is pressed by anoperator in the direction 367. As FIG. 19C illustrates, non-tissueengaging surface 1930, which is smoother than tissue engaging strip1920, reduces disruption of tissue 1950 after it has been separated bytissue engaging strip 1920. Shroud 1940 further protects tissue 1950from disruption by dissecting wheel 1910 as the dissector penetratesfurther into tissue 1950 in the direction of pressing 367.

FIG. 19D illustrates an additional, important action of non-tissueengaging surface 1930 and of shroud 1940. When there is a component ofmotion 1901 in the direction of pressing 367 (not shown here) ofDifferential Dissecting Instrument 1900 into tissue 1950, these widerportions (non-tissue engaging surface 1930 and of shroud 1940) ofDifferential Dissecting Instrument 1900 force apart, or wedge, recentlyseparated portions of tissue 1950, aligning and straining the fibrouscomponents 1980 of tissue 1950, putting them in tension and aligningthem perpendicular to the motion of tissue engaging strip 1920. Thisstrain in fibrous components 1980 facilitates the ability of theprojections of the tissue engaging materials in tissue engaging strip1920 to grab and tear individual fibers.

As tissue engaging strip 1920 moves past tissue 1950, moving in adirection perpendicular to (and so through) the plane of the page, theprojections on tissue engaging strip 1920 therein disrupt tissue 1950,including tearing individual fibrous components 1980 of tissue 1950(e.g. collagen or elastin fibers). Such fibrous components 1980frequently have irregular alignments (i.e., irregular orientations) inSoft Tissues. However, as tissue 1950 is disrupted, DifferentialDissecting Instrument 1900 pushes into tissue 1950 in the direction ofcomponent of motion 1901 such that as remaining tissue engaging surface1930 and shroud 1940 push into the separated tissue 1950, they pushtissue 1950, including severed fibrous components 1990, aside in thedirection of arrows 1960 and 1961, aligning previously irregularlyoriented fibers and straining material at the point of contact of tissueengaging strip 1920. This local region of strain aligns and strains (andso pre-stresses) unsevered fibrous components 1980 in a directionperpendicular to the direction of motion of tissue engaging strip 1920,as shown by double-ended arrow 1970, facilitating their being grabbedand increasing the likelihood of their being severed by projections fromtissue engaging strip 1920. Non-tissue engaging surface 1930 and ofshroud 1940 will act as a wedge if they are angled with respect to oneanother, as shown in FIG. 19C and FIG. 19D or even if they have a widththat is wider than the tissue engaging surface 1910. In one embodiment,a semi-ellipsoid shape, as described in FIG. 3F, in which the secondminor semi-axis C is a significant fraction of the first minor semi-axisB (e.g., in one embodiment, where 0.2B<C<0.8B), is an effective shapefor wedging.

Alignment of fibers, as described in the preceding paragraph, cangreatly alter how a DDM performs. Alignment can be achieved by thesurgeon straining a tissue in the appropriate directions with theirhands or with a separate instrument. Alignment can be achieved by theDDM, as described in the preceding paragraph, by a smooth portion on atissue engaging wheel, such as non-tissue engaging surface 1930 in FIG.19C through FIG. 19D, by a smooth shroud, such as shroud 1940 in FIG.19A through FIG. 19D, or by a separate mechanism on a DDM.

FIG. 20 shows details of one version of disruption of tissue segments ina human patient. The region of interest 2000 of the patient is depictedwithin a circular window, showing a section view through two apposedvolumes, namely a tissue segment A apposed to a tissue segment B; theapposition occurs in a region 2010 bridged by both interstitial fibers2012 and taut interstitial fibers 2015 and further associated withbroken interstitial fibers 2020. Also depicted in the circular window isa DDM 2030 possessing a tissue engaging surface 2034 that furtherpossesses projections 2032 and a smooth non-tissue engaging surface2033. In this view, the DDM 2030 reciprocates about an axis 2036, sothat the motion of the fiber-engaging projections 2032 is in and out ofthe plane of the page (i.e., reciprocally toward and away from theviewer).

Each of the tissue segment A and tissue segment B further has a tissuesegment surface 2005 and a tissue segment surface 2006, respectively,composed of relatively tightly packed fibers aligned parallel to tissuesegment surface 2005 and tissue segment surface 2006, forming amembranous covering over tissue segment A and tissue segment B (e.g.,tissue segments A and B comprise Firm Tissues). Tissue segment A'ssurface 2005 and tissue segment B's surface 2006 are alsothree-dimensionally curvaceous. While these tissue segment surfaces 2005and 2006 may not be in contact with one another at every point, tissuesurface 2005 and tissue segment surface 2006 do meet in a region 2010where tissue segment surface 2005 and tissue segment surface 2006 areapposed in a locally, roughly parallel manner, and are frequentlysubstantially in contact with one another.

In that region 2010, the tissue segment surface 2005 and the tissuesegment surface 2006 are secured to one another by a population ofrelatively loose interstitial fibers 2012 that run substantiallyperpendicularly to the two apposed tissue segment surfaces 2005 and2006. This sparse population of interstitial fibers 2012 may or may notalso be derived from (or be members of) the populations of fiberscomprising the more tightly packed woven surfaces that form the tissuesegment surfaces 2005 and 2006. For example, a given fiber comprisingpart of a tissue segment surface 2005 may run along that surface forsome distance before turning away and continuing across the region 2010,thereby becoming a member of the population of interstitial fibers 2012,and further, may continue across the region 2010 to tissue segmentsurface 2006, where it can turn and interweave therein, thereby becominga member of the population of fibers comprising tissue segment surface2006. Thus, the definition of interstitial fibers 2012 includes anyfibers crossing, bridging, traversing or otherwise connecting (orintimately associated with) the region 2010 where tissue segment surface2005 and tissue segment surface 2006 are in apposition. The interstitialfibers 2012 may be the same type of fibers as those comprising thetissue segment surface 2005 and tissue segment surface 2006 of tissuesegment A and tissue segment B in one embodiment. In another embodiment,the interstitial fibers 2012 may be a distinct type, and theinterstitial fibers 2012 may be strongly or weakly bound, directly orindirectly, to the tissue segment surface 2005 and the tissue segmentsurface 2006.

In each case, all fibers involved are mechanically capable oftransmitting force (via tension) either along the surface of eachindividual tissue segment, or interstitially, between the two tissuesegments, or both. For example, the state of tension of the interstitialfibers 2010 and the fibers comprising the tissue segment surface 2005and the tissue segment surface 2006 depends on the forces that act upontissue segment A and tissue segment B, for example when smoothnon-tissue engaging surface 2033 wedges into and forces apart thesetissue segments in the directions 2040 and 2041. For example, the fibers2010 resist tensile strains that arise from the motion of tissue segmentsurface 2005 in the direction 2040 and the motion of tissue segmentsurface 2006 in the direction 2041 relative to one another, and further,this resistance varies according to the mechanical properties of thefibers. For example, if the unstrained interstitial fibers 2012 arealigned perpendicularly to the two apposed tissue segment surfaces 2005and 2006, then the distance between tissue segment A and tissue segmentB may be increased (as shown by arrow 2030) until the interstitialfibers 2010 first become straightened like the taut interstitial fibers2015, and then finally the fibers may fail, as is shown by the brokeninterstitial fibers 2020. The most common fiber type in humans iscollagen, which possesses a breaking strain of about 5% beyondunstressed normal length. If tissue segment A and tissue segment B aremoved apart as shown by arrow 2030, the collagen fibers (here,unstrained interstitial fibers 2012) will first become taut (as are tautfibers 2015). If the two tissue segments A and B are moved even furtherapart, collagen fibers will stretch about 5%. Crucially, at this point,if tissue segment A is moved further than 5% beyond taut from tissuesegment B, either the taut interstitial fibers 2015 will break, or, ifthe taut fibers 2012 do not break, the tissue segments themselves mayrupture, with deleterious consequences for the patient.

Since surgeons very often must separate, dissever, or otherwise movetissue segments with respect to one another to gain access to variousareas inside patients, surgeons are constantly straining fiberpopulations equivalent to interstitial fibers 2010 throughout patients'bodies. Current practice requires either slicing interstitial fibers tofree one tissue segment from another, or tearing interstitial fiberswholesale by applying blunt force with forceps (by opening the jaws,forcing the tissue segments apart, and so tearing the interstitialfibers). Common complications are either slicing into the tissuesegments while attempting to cut only the interstitial fibers via sharpdissection or tearing off smaller or larger portions of the tissuesegments while attempting blunt dissection of the interstitial fibers.Either approach first strains to tautness the interstitial fibers 2010,then stretches them, and then tears them. The consequences (for example,air leaks and bleeding of segments of the lung) of the aforementionedintimate connection of the interstitial fibers 2010 with the tissuesegment surfaces 2005 and 2006 now becomes clear: one must segregate theforces required to cause the interstitial fibers to fail without alsosubjecting the integrated tissue segments themselves to the same forces.

The embodiments of the Differential Dissecting Instruments disclosedherein are specifically designed to segregate forces on fiberpopulations by generating an initial separating motion of apposed tissuesegments A and B via impingement of the smooth surfaces 2033, thusexposing and tensioning (pre-stressing) individual interstitial fibers2010, making these fibers much more likely to break, exploiting theopportunity provided by these now taut interstitial fibers 2015, andfurther allowing those to be discreetly encountered, engaged andconverted into broken interstitial fibers 2020 by the local impingementof projections 2032 of the tissue engaging surface 2034 of theDifferential Dissecting Member 2030. In this way, a DDM having asmooth-sided non-tissue engaging surface and/or shroud can greatlyincrease both the speed and effectiveness of dissection of tissues whilelimiting the extent of that dissection effect to just those fiberswithin Soft Tissues that connect adjacent regions of Firm Tissues andstill preserving those Firm Tissues.

FIG. 21A through FIG. 21C-4 illustrate another Differential DissectingInstrument 2100 that uses a very thin dissecting wheel 2110 as the DDM.Dissecting wheel 2110 is nearly entirely wrapped in a shroud 2120 toachieve a very thin tissue engaging surface 2009 with shroud 2120 actingto protect, separate and pre-stress the tissue to be dissected, as shownin FIG. 19D.

FIG. 21A shows a side view, and FIG. 21B shows a front view. FIG. 21Ashows a side view of a differential dissecting member that has a thindissecting wheel and is wrapped in a shroud; FIG. 21B-1 and FIG. 21B-2further illustrate a front view of the shrouded differential dissectingmember in FIG. 21A and a close-up view of same, respectively. Dissectingwheel 2110 is mounted on two posts, first post 2130 and second post 2131(seen in side view of FIG. 21B-1) via rotational axle 2135. Rotationalaxle 2135 is free to rotate within first post 2130 and second post 2131,but is firmly affixed to dissecting wheel 2110. Sprocket 2140 is alsofirmly affixed to axle 2135. Sprocket 2140 is turned by drive belt 2150.Thus, a drive mechanism 2160 is created by first post 2130 and secondpost 2131, axle 2135, sprocket 2140, and drive belt 2150 to turndissecting wheel 2110 inside shroud 2120 in the direction of arrow 2161.Alternate drive mechanisms can be used, and motion can either berotational or oscillatory. The first margin 2111 and second margin 2112of dissecting wheel 2110 preferably are not sharp, as shown in theenlarged portion of FIG. 21B-2. (First and second margins 2111 and 2112are like first and second margins 1540 and 1541 in FIGS. 15B-1 through15B-3.) Sharp margins can disrupt more aggressively than a roundedmargin; nevertheless, a sharper margin can be used if more aggressivedisruption or even disrupting is desired. Furthermore, one margin can besharper than the other if a differential disruption or disrupting isdesired. For example, first margin 2111 can be square or even sharp,while second margin 2112 can be rounded to achieve more aggressivedisruption or disrupting on the side of first margin 2111.

Shroud 2120 nearly encloses dissecting wheel 2110, leaving only a fineportion of dissecting wheel 2110 exposed as the tissue engaging surface2111, and forming a wedge angle ω that determines the strain on tissueat the point of disruption of dissecting wheel 2110. Larger wedge anglesω strain tissue more as DDM 2100 is pushed into a tissue. FIGS. 21C-1through 21C-4 depict DDM 2100 with shroud 2120 in four differentpositions. Shroud 2120 can be moved independently of drive mechanism2160 and dissecting wheel 2110, shroud 2120 being able to move in thedirection of double headed arrow 2190. Thus, in Position 1 (FIG. 21C-1)only a thin portion of dissecting wheel 2110 is exposed. In Position 2(FIG. 21C-2), shroud 2120 has been moved in the direction of arrow 2191,leaving a thinner portion of dissecting wheel 2110 exposed and alsocreating a larger wedge angle ω. In Position 3 (FIG. 21C-3), shroud 2120has been moved in the direction of arrow 2192 such that shroud 2120completely encloses dissecting wheel 2110. Thus, dissecting wheel 2110can no longer disrupt tissue. In this position, the dissecting wheel2110 effectively acts as a smooth, flat, blunt probe. In Position 4(FIG. 21C-4), shroud 2120 has moved in the direction of arrow 2193,increasing the exposure seen in Position 1 or Position 2 of dissectingwheel 2110 and decreasing wedge angle ω.

FIG. 22 shows the distal end of a differential dissector 2210, includingone embodiment of a reciprocating mechanism, here a scotch yoke. Thedistal end of differential dissector 2210 includes a housing 2212, whichfurther contains a pivot bearing 2214, a motor shaft bearing 2216, and ashaft drum bearing 2218. FIG. 22 also shows a motor shaft 2220, a shaftdrum 2222 coaxial with and affixed to the motor shaft 2220, and a driverpin 2224 which may be parallel but not coaxial to motor shaft 2220, andis itself affixed to the shaft drum 2222. Further, there is aDifferential Dissecting Member, DDM 2230, which is associated with thedifferential dissector housing 2212, and further comprises an outersurface 2231 defining the body of the DDM 2230, a tissue engagingsurface 2232 forming at least a portion of the outer surface 2231, a DDMpivot shaft 2234 that fits into the pivot bearing 2214, and furthercomprises a hollow DDM pin follower 2236 that effectively captures thedriver pin 2224. The internal three-dimensional shape of the hollow DDMpin follower 2236 is here shown as a prism, so that in the view shown inFIG. 22 the cross-sectional shape resembles an hourglass, whileperpendicular to that view, the cross-sectional shape is rectilinear.

FIG. 23A, FIG. 23B, and FIG. 23C show a sectional view of a portion ofthe DDM 2230 of FIG. 22 through the narrowest portion of the waist ofthe hourglass-shaped hollow DDM pin follower 2236 and perpendicular tothe rotational axis of the shaft drum 2222. The shape of the DDM pinfollower 2236 is in this view rectangular; further, in this view showingthe dimensions through the waist of 2236 the height of the rectangle isequal or larger than a diameter described by the outer diameter of thedriver pin 2224 along its circular path 2237. The width of the rectanglein this view corresponds to the outer diameter of the driver pin 2224.The DDM 2230 containing the hollow DDM pin follower 2236 rotates aboutthe axis 2233 of the shaft 2234. Thus, the position of the hollow DDMpin follower 2236 and so the rotational position of the DDM 2230 isdetermined by the rotational position of the driver pin 2224.

In operation, referring to FIG. 22, along with FIGS. 23A-23C, the motor(not shown) turns the motor shaft 2220, which turns the drum 2222 aboutits axis of rotation, which causes the driver pin 2224 to travel about acircular path 2237, the plane of which is here perpendicular to therotational axis of the drum 2222. As in a scotch yoke, the rectangularlyhollow DDM pin follower 2236 converts the circular path 2237 of thedriver pin 2224 into linear travel 2238 of the hollow DDM pin follower2236; given that the pin follower 2236 is located some distance awayfrom the axis 2233, the DDM 2230 is leveraged about the axis 2233, soconverting the rotational path 2237 into linear travel 2238 and soreciprocating motion of the DDM 2230 rotating about the DDM pivot shaft2234 held by the pivot bearing 2214. The pattern of the reciprocalmotion of the DDM 2230 can be controlled by varying the shape of thehollow DDM pin follower 2236, the driver pin 2224, the 3D angle of theaxis 2233 about which the shaft 2234 rotates, the distance from thedriver pin 2224 to the axis 2233, and also by varying the rotationalspeed of the motor.

The DDM 2230 of FIG. 22 may have reciprocating motion 2250 and 2251, asshown in side view in FIG. 24A and FIG. 24B. The oscillation sequenceshown depicts the extreme positions of the DDM 2230 as the driver pin2224 travels about circular path 2237 when provided with rotationalmotion 2299 from the motor (not shown). The action of the tissueengaging surface 2232 of the DDM 2230 on the surface of the tissues tobe dissected is best shown in an edge-on view in FIG. 20.

A surgeon operating inside a patient desires to create the least traumapossible to tissues which are not the focus of the procedure, or aresimply in the way of the Target Tissue. To this end, FIGS. 25A through25C depict the profile view of an embodiment of a largely shrouded DDMassembly 2500, further comprising a shrouded pivot shaft 2510 thatprojects perpendicularly to the page (i.e., at the viewer), an internalmotor shaft 2550, an internal driver drum 2522, a driver pin 2524, a DDIhousing 2512, a DDM 2520 that reciprocates about the shrouded pivotshaft 2510 (and so within the plane of the page), a tissue engaging DDMsurface 2534, a smooth DDM surface 2518, a substantially circular DDMregion 2516, a shroud margin 2517, and a shroud-DDM gap 2514. Consideredas a whole, with all exterior surfaces of the DDM assembly 2500 includedas one, a shrouded DDM assembly 2500 presents a nearly continuous smoothsurface to a patient's tissues. In this regard, other than the limitedextent of the tissue engaging DDM surface 2534, the entire DifferentialDissecting Instrument fitted with the DDM assembly 2500 acts likenothing more than a polished probe.

Once activated, the DDM 2520 reciprocates within and relative to thehousing 2512. At the edge of the housing 2512 closest to the DDM 2520 isthe shroud margin 2517. Between the shroud margin 2517 and the DDM 2520is found the shroud-DDM gap 2514. In one embodiment, a DifferentialDissecting Instrument fitted with a DDM assembly 2500 includesprovisions for preserving the outwardly smooth character of theDifferential Dissecting Instrument. The shroud-DDM gap 2514 thuspresents a challenge, in that any relative motion of the DDM 2520 withrespect to the housing 2512 could enlarge the shroud-DDM gap 2514,presenting sharp edges to the tissues. Alternatively, a portion of theDDM 2520 could impact the housing 2512. Also, in one embodiment, theshroud-DDM gap 2514 is kept as small as possible at all times. Tofacilitate this, the DDM 2520 has a circular DDM region 2516, defined inthis perspective as a portion of the mass of the DDM 2520 having thecross-section of a circle with its center coincident with the axis ofthe shrouded pivot shaft 2510. This circular DDM region 2516 defines andoccupies that portion of the outer surface of the DDM 2520 that passesthe shroud margin 2517 during reciprocating motion of the DDM 2520, andat a distance that defines the shroud-DDM gap 2514. Because the circularDDM region 2516 preserves over the angle of rotation the same radius ofDDM 2520, this preserves the shroud-DDM gap 2514 at a constant value(i.e., shroud-DDM gap 2514 does not change despite motion of the DDM2520). Thus, the Differential Dissecting Instrument that is fitted withthis DDM assembly presents to the tissues a continuously smooth surfaceeverywhere through time.

FIG. 25D depicts an oblique view of the largely shrouded DDM assembly2500, showing a housing 2512, a DDM 2520 that reciprocates about theshrouded pivot shaft 2510 (see FIGS. 25A through 25C), a tissue engagingDDM surface 2534, a smooth DDM surface 2518, a substantially circularDDM region 2516, a shroud margin 2517, and a shroud-DDM gap 2514.

Sharp dissection is frequently performed alternately with bluntdissection when exposing a Target Tissue. This occurs whenever amembrane or a large fibrous component, which resists blunt dissection,is encountered and must be severed for the surgeon to penetrate furtherinto a tissue. Current practice requires that a surgeon either use asuboptimal instrument for blunt dissection (e.g., an inactiveelectrosurgery scalpel) or to swap instruments while exposing a TargetTissue. Use of a suboptimal instrument decreases the ease of bluntdissection and increases potential risk to a Target Tissue. Swappingconsumes time and is distracting, especially for many minimally invasiveprocedures in which the instrument must pass through a narrow orifice inthe body wall and then be gently guided to the site, such as duringlaparoscopy and thoracoscopy. A Differential Dissecting Instrument canbe equipped with a sharp dissecting component that can be selectivelyactivated by a surgeon, eliminating the need for instrument swappingwhile still providing the surgeon with an optimal instrument.

FIGS. 26A-1 and 26A-2 show a top and side view, respectively, of oneembodiment of a Differential Dissecting Instrument 2600, similar toDifferential Dissecting Instrument 2000, as shown in FIG. 20, but nowalso comprising a retractable scalpel blade that is covered during bluntdissection. FIG. 26A-1 and FIG. 26B-1 show side views while FIG. 26A-2and FIG. 26B-2 show top views; FIG. 26A-1 and FIG. 26A-2 show thedifferential dissecting member with a retractable scalpel withdrawn. Theretractable scalpel blade can be projected outward by a surgeon forsharp dissection and then retracted before proceeding with further bluntdissection. Differential Dissecting Instrument 2600 has an elongatemember comprised of shroud 2620 to which DDM 2610 is rotatably mountedvia rotational axle 2635. To one side of DDM 2610 is a slot 2612 underwhich lies retractable scalpel blade 2622 such that retractable scalpelblade 2622 is completely covered by shroud 2620. Retractable scalpelblade 2622 is actuated by a retraction mechanism (not illustrated)controlled by a surgeon. Actuation of the retractable scalpel blade 2622can be controlled manually via a slider, by electrical actuation (suchas a solenoid), or by any suitable mechanism controllable by anoperator.

FIGS. 26B-1 and 26B-2 show Differential Dissecting Instrument 2600 withretractable scalpel blade 2622 extended for sharp dissection. FIG. 26B-1and FIG. 26B-2 show the same differential dissecting member with theretractable scalpel extended. Retractable scalpel blade 2622 is oneexample of a sharp dissecting tool. In other embodiments, theDifferential Dissecting Instrument 2600 could include other sharpdissection tools, such as an electrosurgery blade, ultrasonic cutter, ora disrupting hook. In other embodiments, the Differential DissectingInstrument 2600 could include a tool for energetic disruption, forexample an electrocautery blade or electrosurgery head. Additionally,instead of retraction, retractable scalpel blade 2622, or other suitabletool, could be selectively be exposed for use by one of severalmechanisms, such as by pop-out, by unfolding, or other mechanism knownin the art.

FIGS. 27A and 27B show a top and side view, respectively, of anotherembodiment of a Differential Dissecting Instrument 2700, similar toDifferential Dissecting Instrument 2600 shown in FIG. 26A and FIG. 26B,but now possessing a grasping member to allow the DifferentialDissecting Instrument 2700 to also function as forceps. DifferentialDissecting Instrument 2700 has a DDM 2710 rotatably attached to aninstrument shaft 2720 and is rotated by a motorized mechanism (notshown). A push rod 2730 is inside instrument shaft 2720 and is activatedby a mechanism residing in a handle (not shown) and activated manuallyby an operator. When DDM 2710 is active, it oscillates back-and-forth asindicated by arrow 2740. When the operator switches off the action ofDDM 2710, the operator can then push with push rod 2730 on forceps jaw2750 which has a control horn 2760 that causes forceps jaw 2750 torotate around pivot point 2770 and thus to open. The opposing jaw forthe forceps is the DDM 2710. The operator can then grasp and releaseobjects between forceps jaw 2750 and DDM 2710 by pushing or pulling onpush rod 2730.

FIG. 28, and FIGS. 29A through 29D depict another embodiment of a DDM.In practice, this embodiment has provided great differential action andrapid dissection through complex tissues. For this embodiment of a DDM,the projections of the tissue engaging surface are formed by valleys cutinto the surface of the DDM. Referring to FIG. 28, DDM 2800 has a firstend 2810 and a second end 2820, with a central axis 2825 connecting thefirst end 2810 and second end 2820. First end 2810 is directed away fromthe complex tissue to be dissected (not shown) and is engaged with adrive mechanism (not shown) that moves DDM 2800 such that second end2820 sweeps along a direction of motion. Here, the mechanism oscillatesDDM 2800 about an axis of rotation 2830 that is perpendicular to thecentral axis 2825 such that the direction of motion 2840 is an arc ofmotion lying in a plane perpendicular to the axis of rotation 2830. Thesecond end 2820 has a tissue-facing surface 2850 that is directed towardthe complex tissue comprising at least one tissue engaging surface 2860and at least one lateral surface 2870.

The motion of DDM 2800 in this example is a reciprocal (back-and-forth)oscillation, but other DDMs can have a continuous rotation or arectilinear motion. The rotation is preferably between 2,000 and 25,000cycles per minute, but can range from 60 cycles per minute up to 900,000cycles per minute, all of which are well below ultrasonic. In certainembodiments, speeds of 300 to 25,000 cycles per minute have been foundto be very effective.

FIGS. 29A through 29E-2 show magnified views of the tissue-facingsurface 2850 of DDM 2800 from FIG. 28. FIG. 29A shows an oblique view oftissue-facing surface 2850 with components identified. FIGS. 29B-D showdifferent views of tissue-facing surface 2850 with the geometry of theshape better described, especially with respect to components oftissue-facing surface 2850. FIG. 29C-2 depicts a close-up of the cornerof a projection shown in FIG. 29C-1; FIG. 29E-1 and FIG. 29E-2 show twoalternative versions of arrangements of valleys and projections formingthe surface of a differential dissecting member. Finally, FIGS. 29E-1and 29E-2 show different embodiments of some of these components. Thetissue-facing surface 2850 has a tissue engaging surface 2860 and twolateral surfaces, a first lateral surface 2871 disposed lateral to andto one side of the tissue engaging surface 2860 and a second lateralsurface 2872 disposed lateral to and to the opposing side of the tissueengaging surface. Referring to FIGS. 29A, 29C-1, and 29C-2, the tissueengaging surface 2860 is comprised of an alternating series of at leastone valley 2910 and one projection 2920 arrayed along the direction ofmotion 2840 which is an arc of motion on the tissue-facing surface 2850such that the intersection of the at least one valley 2910 and at leastone projection 2920 define at least one valley edge 2930 oriented suchthat it has a component of direction perpendicular to the direction ofmotion 2840.

No valley edge 2930 should be sharp, e.g. it should not be capable ofslicing into Complex Tissue, especially into Firm Tissue. For example,no point on a valley edge 2930 should have a radius of curvature R_(c)smaller than approximately 0.025 mm (see FIG. 29C-1, expanded view).This radius of curvature R_(c) is similar to the radius of curvature ofthe surface R_(s) and of the edge R_(e) as depicted in FIG. 15. We haveshown through testing that edges with radius of curvature R_(c) nosmaller than approximately 0.050 mm can be effective, too. Additionally,the radius of curvature R_(c) can vary along the length of valley edge2930. In the embodiment shown in FIGS. 29A through 29D, the radius ofcurvature R_(c) is smallest where the valley edge 2930 is furthest fromthe axis of rotation 2830 and increases closer to the first lateralsurface 2871 and the second lateral surface 2872. Furthermore, theminimum radius of curvature R_(c) for a valley edge 2930 can bedifferent for different valley edges in the same DDM and even for thevalley edges on opposing sides of the same valley.

Projections 2920 in DDM 2800 may be formed by subtractive manufacture inone embodiment. In effect, the valleys 2910 are cut out of the surfaceof a semi-ellipsoid, as shown in FIGS. 29B, 29C-1, and 29C-2, having amajor semi-axis A aligned perpendicular to the rotational velocity 2830and parallel to the central axis 2825 (see FIG. 28) (i.e. pointingtoward the Complex Tissue), a first minor semi-axis B, and a secondminor semi-axis C that is parallel to the rotational velocity 2830. Theprojections 2920 thus have projection tops 2940 that are the remainingsemi-ellipsoidal surface and are continuous with the lateral surfaces2971 and 2972. Tissue engaging surfaces 2860 are thus created by thelateral limits of the valleys 2910 in this embodiment and span thetissue-facing surface between the valleys 2910 that form the projection2920. In other embodiments, projections can be formed by other means andcan thus have more differently shaped projection tops, includingprojection tops that are not formed as the remainder of a surface. Forexample, in one embodiment, the projections can effectively be built upfrom a surface, enabling more complex projection tops.

Referring to FIG. 29A, FIGS. 29C, and 29C-2, each valley 2910 may have afirst valley side 2911, a second valley side 2912, and a valley bottom2913, whereby the first valley side 2911 and the second valley side 2912lie on opposing sides of the valley 2910. The valley bottom 2913 islinear or curvilinear and can be two-dimensional or 3-dimensional. Forexample, the valley bottoms in DDM 2800 are straight lines alignedparallel to the rotational velocity 2830. The first valley side 2911 andthe second valley side 2912 rise from the valley bottom 2913 to a valleyedge 2930. The transition from valley bottom can be gradual andindeterminate, as in the valleys 2910 in DDM 2800, or the transition canbe faceted. A valley 2910 may be curved in two dimensions, beingstraight in the direction parallel to the valley bottom 2913 (and thusalso parallel to the axis of rotation 2830). Valley sides, however, canbe any shape, including surfaces curved in three dimensions.

A valley edge is formed by the intersection of a valley wall with aprojection top. Valley edges can thus have different shapes, dependingon the shapes of the projection top and the valley edge. The valleyedges 2930 on DDM 2800 trace three dimensional curves and thus have bothcurvature and torsion (as defined mathematically in geometry) that arenon-zero and varying along the valley edge. Valley edges can havesmoothly varying curvature and torsion (as do valley edges 2930), or avalley edge can be bent.

FIG. 29C-1 presents an expanded view of a valley edge, in the planeperpendicular to the valley edge. The projection top 2920 and the valleyside (2911 or 2912 here) form a face angle Γ in this plane that isrounded at the intersection (i.e. it is “radiused” as a machinist woulddescribe it) having the radius of curvature R_(c) described above. Theface angle Γ can form an angle less than 90°, which appears sharp onfirst inspection, but sharpness is determined by the radius of curvatureR_(c) of the edge. The face angle Γ can vary along the length of thevalley edge, as it does for DDM 2800 where the face angle Γ is smallestat the points on the valley edge furthest from the axis of rotation2830. In one embodiment, face angles of about thirty degrees) (30° toabout one hundred fifty degrees (150°) may be effective.

Valleys have a length, width, and depth where the valley length is thelength of the valley bottom, the valley width is the distance separatingthe valley edges of one valley measured at their longest distance ofseparation, and the valley depth is the maximum vertical distance from avalley edge to the valley bottom (e.g. peak-to-trough height). Typicaldimensions for a valley include valley lengths of 0.25 mm to 10 mm,valley widths of 0.1 mm to 10 mm, and valley depths of 0.1 mm to 10 mm.In one embodiment, a valley length of approximately three (3) mm, avalley depth of approximately three (3) mm, and a valley width ofapproximately two (2) mm has been found to be very effective.

When a DDM has multiple valleys, like DDM 2800, the valleys can beparallel, like valleys 2910 of DDM 2800, having valley bottoms 2913 thatare all parallel, or they can be non-parallel with valley bottoms lyingat non-zero angles with respect to each other or at variable angles withrespect to each other.

The valleys 2910 of DDM 2800 have a single channel (the space bounded bythe valley sides and valley bottom); however, valleys can have multiple,intersecting channels such that valley bottoms can fork or multiplybranch or form networks on the tissue engaging surface. FIGS. 29E-1 and29E-2 show top views of two DDMs, the left DDM 2980 having parallelvalleys 2981 with valley bottoms that are not parallel to the rotationalvelocity while the right DDM 2990 has network 2991 of multipleintersecting valleys all at different angles with respect to therotational velocity and to each other.

As described above, the tissue-facing surface 2850 of DDM 2800 has thesurface of a semi-ellipsoid having a major semi-axis A alignedperpendicular to the axis of rotation 2830 and parallel to the centralaxis 2825, a first minor semi-axis B, and a second minor semi-axis Cthat is parallel to the axis of rotation 2830. Tissue-facing surface2850 may have an ellipsoid shape in one embodiment, in which A>B>C.However, any relationship is possible between the lengths of thesemi-axes. For example, in other embodiments, DDMs may be fabricated forwhich A=B=C (e.g., the tissue-facing surface is hemi-spherical).

The first lateral surface 2871 and the second lateral surface 2872 ofDDM 2800 are continuations of the hemi-ellipsoidal shape. As such, theylie at an angle to one another, forming a wedge, as earlier depicted inFIG. 19D and FIG. 20, that aligns and strains fibrous components of aComplex Tissue allowing the projections to snag and break the fibrouscomponents.

FIG. 30A presents the situation of a first tissue region 3011 encased infirst membrane 3016 and second tissue region 3012 encased in secondmembrane 3017. First membrane 3016 and second membrane 3017 abut attissue plane 3020. First membrane 3016 and second membrane 3017 areformed of densely packed fibrous components and thus comprise a FirmTissue. The interstitial materials spanning the tissue plane from firstmembrane 3016 to second membrane 3017 include fibrous components 3030.These fibrous components 3030 are less densely packed, so theinterstitial materials comprise a Soft Tissue. As tissue-facing surface2850 is pressed in the direction of arrow 3050 into the tissue plane3020 to separate the two tissue regions 3011 and 3012, the first lateralsurface 2871 and the second lateral surface 2872 exert a first spreadingforce 3041 and a second spreading force 3042 on tissue regions 3011 and3012, respectively, that align and strain fibrous components 3030 at theprojection tops 2940 (see FIGS. 29C-1 and 29C-2). This enables thefibrous components 3030 to enter the valleys 2910 and thus be snaggedand then torn by a projection 2920 as the tissue-facing surface 2850rotates about axis of rotation 2830 and so moves out of the plane of thepage (toward the viewer). Additionally, as the projection tops 2940 arecontinuous with the lateral sides, the more lateral areas of theprojection tops 2940 also exert additional spreading forces 3043 and3044 that also wedge tissue regions 3011 and 3012 apart, furtherincreasing the strain on fibrous components 3030.

FIGS. 30B through 30D show how the curvature of first lateral surface2871 and second lateral surface 2872 can be changed to make a DDM moreor less aggressive. Consider first DDM 3060 in FIG. 30B. As explained inFIG. 30A, the more lateral areas of the projection tops 2940 exertspreading forces 3043 and 3044 that wedge adjacent tissue regions apart.Furthermore, the first lateral surface 2871 and the second lateralsurface 2872 exert a first spreading force 3041 and a second spreadingforce 3042. As first angle 3065 formed by spreading forces 3043 and 3044approaches 180° (as shown for DDM 3061 in FIG. 30C), the wedging actionof the lateral areas of the projection tops 2940 decreases. (Note thatangle 3065 is similar to the wedge angle ω described in FIGS. 21Athrough 21C.) If projections 2920 become also laterally (left-right inthis figure) thinner, then the projections will more rapidly disruptSoft Tissue but will also be more proned to abrade or disrupt FirmTissue. As in FIG. 30A, first and second lateral surfaces 2871 and 2872create spreading forces 3041 and 3042, respectively, forming a secondangle 3066 (effectively, a second wedge angle ω). If second angle 3066is similar to first angle 3065 (as shown for DDM 3060 in FIG. 30B), thenthese surfaces combine to create a single wedging surface. If, as inFIG. 30C, second angle 3066′ is larger than first angle 3065 (i.e.lateral surfaces 2871 and 2872 are more nearly parallel), then secondangle 3066′ exerts little or no wedging action. Conversely, if, as inFIG. 30D, second angle 3066″ is smaller than first angle 3065 (i.e.lateral surfaces 2871 and 2872 become more nearly perpendicular, thensecond angle 3066″ exerts a greater wedging action. DDMs like 3061 haveproven more effective in dissecting tissue planes possessing prominentcollagen fibrils that span the tissue plane, crossing from one surfaceto the other.

Referring back to FIG. 30A, FIG. 30A also illustrates an importantaspect of a DDM. A DDM will automatically follow a tissue plane. Becausetissue planes tend to be bounded by Firm Tissues (e.g. membranes, ducts,etc.) and are spanned by Soft Tissues, a DDM will, by virtue of itsdifferential action, not move into the Firm Tissue and will move intothe Soft Tissue, thus following and separating a tissue plane willlittle or no guidance from an operator. This means that the operatorneed not have as detailed an understanding of the anatomy as is requiredby current practice or, conversely, a DDM allows a skilled surgeon tomore confidently dissect an uncertain anatomy, e.g. when tissue planesare distorted by a tumor or when tissues are swollen or inflamed.

FIG. 31 shows an end-on view of the tissue-facing surface 2850 as itsnags and then stretches to breaking the fibrous components 3030 shownin FIG. 30A. Three fibrous components (first fibrous component 3031,second fibrous component 3032, and third fibrous component 3033) havebeen snagged by three projections (first projection 2921, secondprojection 2922, and third projection 2923, respectively). Tissue facingsurface 2850 rotates, generating a direction of motion 2840 which is anarc of motion as depicted by arrows 3100. First fibrous component 3031has just entered the first valley 2911 and has not yet been snagged byfirst projection 2921. Second fibrous component 3032 entered the secondvalley 2912 at an earlier point in time and has been snagged andstrained by second projection 2922. Third fibrous component 3033 enteredthe third valley 2913 at an even earlier point in time and has beensnagged and strained even further by third projection 2923. Ultimately,all three fibrous components 3031, 3032, and 3033 will be strained tobreaking.

FIG. 31 illustrates an important aspect of DDM 2800's design. Becausethe valleys span from one lateral surface 2871 to the opposing lateralsurface 2872, each valley creates an open space spanning across the endof DDM 2800 into which strained fibrous components can enter, thusfacilitating their being snagged by the projections.

It is important to note that DDM 2800 does not have arrays of smallprojections that give any part of its surface texture, as describedearlier. Rather, all surfaces of DDM 2800 are smooth and, preferably,possess low friction surfaces. The shapes and configurations of thesurface features of DDM 2800 are responsible for its ability todifferentially dissect Complex Tissues. In fact, DDM 2800 works bestwhen all of its surfaces that are in contact with tissue are welllubricated with, for example, a surgical lube.

FIG. 32 shows an exploded view of one embodiment of a completedifferential dissecting instrument. The differential dissectinginstrument 3200 is grossly comprised of an instrument handle 3212 fromwhich projects an instrument insertion tube 3290 which has a first end3291 attached to instrument handle 3212 and a second end 3293, to whichis rotatably mounted a DDM 3292. The instrument handle 3212 is assembledfrom an upper housing 3220, which includes upper battery cover 3222, anda lower housing 3230, which are held together by instrument housingbolts 3236. Included in the upper housing 3220 and lower housing 3230are a motor 3260 and a battery pack 3270. In the upper housing 3220 is aswitch port 3224, through which can be accessed a switch 3282 (which maybe a momentary switch or an on-off switch) for providing power to themotor 3260 from the battery pack 3270. A printed circuit board 3280further containing a power level adjustment 3281 (which can be anyconvenient component, but is here shown as a linear potentiometer) isprovided and can be accessed through a flexible switch cover 3284mounted in surface of the upper housing 3220. Also included are forwardspring battery connectors 3272 and aft spring battery connectors 3274,which route electric power from the battery pack 3270. The upper housing3220 further contains an instrument insertion tube support 3226 tosecure and orient the instrument insertion tube 3290 near and coaxialwith the motor 3260.

The lower housing 3230 further provides access to and secures thebattery pack 3270 with an integral lower battery cover 3232 and motorhousing section 3234, further held to the upper housing 3220 using thethree instrument housing bolts 3236. The motor housing section 3234holds and secures the motor 3260 coaxial with the instrument insertiontube 3290, which passes through the instrument insertion tube support3226. The motor 3260 is pressed forward by the motor housing section3234 against the motor collar 3264, the inside diameter of which leavesroom for the motor shaft coupler 3262. The motor shaft coupler 3262,with the help of the motor shaft coupler bolts 3266, mounts securelyonto the end of the shaft of the motor 3260 and further grips a firstend 3295 of a drive shaft 3294. The drive shaft 3294 is rotated by themotor 3260 inside of and concentrically with the instrument insertiontube 3290. The drive shaft 3294 also has a second end 3297 of driveshaft 3294, which is concentrically supported by a shaft bearing 3296that is mounted onto a second end 3293 of instrument insertion tube3290. The DDM 3292 is rotatably mounted onto shaft bearing 3296 suchthat drive shaft 3294 causes DDM 3292 to rotate. DDM 3292, shaft bearing3296, drive shaft 3294, and instrument insertion tube 3290 collectivelyform the DDM assembly 3299, which is described next.

FIG. 33A, FIG. 33B, and FIG. 33C depict the details of the DDM assembly3299, including how the DDM 3292 is assembled with other components suchthat the motor 3260 drives oscillation of DDM 3292.

Referring now to FIG. 33A, DDM 3292 in this embodiment comprises atissue facing surface 3322 on a first end 3321 and a shaft bearing grip3324 on a second end 3323. The shaft bearing grip 3324 is further fittedwith two pivot pins 3325. The DDM 3292 may be partially hollow,possessing a shaft bearing cavity 3326 that permits the shaft bearing3296 to fit inside. The shaft bearing cavity 3326 further sports a camfollowing cavity 3328. The shape of the cam following cavity 3328 may beoblong in that it is much narrower in one direction, forming a slot.Shaft bearing 3296 has a bore 3336, a shaft bearing tip 3332, a threadedbearing end 3338, and two pivot pin holes 3334. Threaded shaft bearingend 3338 screws into threaded shaft bearing mount 3342 on the second end3293 of instrument insertion tube 3290. Bore 3336 can have a diametergreater than the diameter 3385 of drive shaft 3294 everywhere along itslength, except at shaft bearing tip 3332, thereby decreasing the contactsurface between shaft bearing 3296 and drive shaft 3294. The second end3297 of drive shaft 3294 is modified to include a main shaft section3352 and a cam shaft section 3354. The various sub-components of thesecomponents allow for their assembly and operation, as can be seen inFIG. 33B and FIG. 33C.

Referring now to FIG. 33B, drive shaft 3294 is shown as fittingcoaxially within shaft bearing 3296 and instrument insertion tube 3290of the DDM assembly 3299. This aligns threaded bearing end 3338 of shaftbearing 3296 for screwing into the threaded shaft bearing mount 3342located at the second end 3293 of instrument insertion tube 3290. Ashaft bearing tip 3332 accommodates drive shaft 3294, preventingmisalignment with respect to the DDM 3292. The second end 3293 of driveshaft 3294 emits from shaft bearing tip 3332 such that cam shaft section3354 is fully exposed. Once the instrument insertion tube 3290, shaftbearing 3296, and drive shaft 3294 are assembled, the DDM 3292 mountsonto shaft bearing 3296 such that (a) the pivot point pins 3325 insertinto pivot pin holes 3334 and (b) cam shaft section 3354 inserts intocam following cavity 3328, as shown in FIG. 33C.

FIG. 33C depicts the assembled DDM assembly 3299. The DDM 3292 fits overthe shaft bearing 3296, which is screwed into the threaded shaft bearingmount 3342 of the instrument insertion tube 3290, all of which coaxiallyencompass the drive shaft 3294. It is notable that the pivot pins 3325on the shaft bearing grip 3324 fit into the pivot pin holes 3334 of theshaft bearing 3296. This arrangement, combined with the shaft bearingcavity 3326, allows the hollow DDM 3292 to rotate freely on the pivotpins 3325. Rotation of drive shaft 3294 causes cam shaft section 3354 torotate inside cam following cavity 3328, driving DDM 3292 to oscillateabout the pivot pin holes 3334 and sweeping tissue facing surface 3322side-to-side as indicated by double sided arrow 3377.

In operation, referring to FIG. 32 and FIGS. 33A through 33C, a surgeonholds the differential dissecting instrument 3210 by the instrumenthandle 3212 and orients the distal tip sporting the DDM 3292 toward thecomplex tissue to be dissected. The surgeon selects the power level bysliding the power level adjustment 3281 to the desired position and thenplaces his or her thumb upon the switch 3282 and presses it to close theswitch. When switch 3282 closes, motor 3260 is turned on and rotates themotor shaft coupler 3262 and, in turn, the drive shaft 3294. The driveshaft 3294 is held coaxially and quite precisely in place by the shaftbearing 3296 and especially the shaft bearing tip 3332, so that the camshaft section 3354 of the drive shaft 3294 oscillates rotationallyinside the cam following cavity 3328 of the shaft bearing cavity 3326 ofthe DDM 3292. The cam following cavity 3328 is oblong, and in theembodiment shown in FIGS. 33A through 33C has its narrowest dimensionoccurring in the direction perpendicular to the axis of the rotationaljoint formed by the pivot pins 3325 and the pivot pin holes 3334. Inthis embodiment, the narrowest dimension of the cam following cavity3328 just barely permits the passage of the cam shaft section 3354 ofthe now rotating drive shaft 3294. Accordingly, the rotationaloscillation of the cam shaft section 3354 impinges on the long walls ofthe cam following cavity 3328, forcing the entire DDM 3292 to rotatethrough an oscillation arc 3377 lying in a plane perpendicular to theaxis of the rotational joint formed by the pivot pins 3325 and the pivotpin holes 3334. In this embodiment, the amplitude of the oscillation arc3377 through which the tissue facing surface 3322 of the differentialdissecting member 3292 swings is a function of the diameter 3385 of thedrive shaft 3294 out of which the cam shaft section 3354 is cut and thedistance 3379 separating tissue facing surface 3322 and pivot pin holes3334. The frequency of the oscillation matches the frequency of theoscillation of rotation of the motor 3260. The operator may control theoscillation frequency of the tissue facing surface 3322 by varying theposition of the power level adjustment 3281. Note that this mechanismfor converting rotation of motor 3260 and thus rotation of drive shaft3294 into oscillation of the DDM 3292 is similar to the scotch yokedepicted in FIGS. 22 through 25C.

Differential Dissecting Instrument 3200 is one example of implementationof a DDM, and many variants are possible. For example, oscillation of aDDM can be driven by a crank and slider mechanism with the slider movingback-and-forth longitudinally inside an instrument insertion tube.Alternatively, a motor could be placed adjacent to the DDM, with themotor shaft directly driving the DDM and only electrical wires to powerthe motor running down the instrument insertion tube. Additionally,because a DDM adapts well to the end of a tube, greatly lengthening theinstrument insertion tube allows differential dissecting instruments,such as Differential Dissecting Instrument 3200, for example, to belaparoscopic instruments. Differential Dissecting Instruments withinstrument insertion tubes as long as thirty-six (36) cm may be used,although longer or shorter tubes are easily accommodated in the design.DDMs as disclosed herein can easily be adapted to the arm of a surgicalrobot, such as the Da Vinci Surgical Robot from Intuitive Surgical(Sunnyvale, Calif.). A DDM can be made very small; for example,effective Differential Dissecting Instruments in which the DDM andinstrument insertion tube fit through a five (5) mm hole, such as asurgical port, can be built, enabling minimally invasive surgery. Thesesmaller devices are easily built.

Further, Differential Dissecting Instruments can be used in which thedrive shaft is replaced by a flexible drive shaft, and the instrumentinsertion tube is curved. This creates Differential DissectingInstruments with curved instrument insertion tubes, like that shown inFIG. 6C. Articulation of the instrument insertion tube is also possible,using for example a drive shaft having a universal joint or otherbendable coupler at the articulation.

As previously disclosed, additional functionality can be added to theend of a Differential Dissecting Instrument. For example,

-   -   FIG. 11B and FIG. 13 show how the design of the DDM permits        fluids to be delivered to a DDM for irrigation, or how suction        can be applied to clear the surgical field, or how a light        source can be placed on or near a DDM to illuminate the surgical        field.    -   FIG. 26A through FIG. 26D disclose a Differential Dissecting        Instrument having an retractable cutting blade that can be made        sharp for cutting or can be energized by a electrosurgical        generator (unipolar or bipolar) for electrosurgery,    -   FIGS. 27A and 27B show how the design of the DDM permits a DDM        to be adapted to function as forceps.

Additional functionality can readily be added to a DifferentialDissecting Instrument. For example, a patch of any size on the side of aDDM or a shroud holding a DDM can be energized such that the patch canbe used for electrocautery. To simplify fabrication, the drive shaft canbe used to conduct the electricity from the handle to the DDM. Thedesign of the DDM permits the forceps shown in FIGS. 27A and 27B toinstead be used as scissors. Additional functionalities can include avideo camera for imaging or ultrasonic surgery for sharp dissection. Theimproved design of the DDM permits many of these additionalfunctionalities to be combined together in one Differential DissectingInstrument. Advantages realized from combining functionalities with aDDM at the working end of a Differential Dissecting Instrument include:reducing the number of instruments a surgeon needs for a procedure;simplifying inventory for the hospital and logistics for support staff;and, most importantly, reducing instrument changes during surgery, whichslow surgery and are a major source of surgical complications. This isespecially true in laparoscopic and robotic surgeries, which requirepositioning instruments into the body through small incisions,frequently with airtight ports.

FIG. 34 shows an oblique view of one embodiment of an assembledDifferential Dissecting Instrument. The Differential DissectingInstrument 3400 is grossly comprised of an instrument handle 3412 fromwhich projects an instrument insertion tube 3490 which has a first end3491 attached to instrument handle 3412 and a second end 3493, to whichis rotatably mounted a DDM 3492. The instrument handle 3412 is assembledfrom an upper housing 3420, which includes upper battery cover 3422, anda lower housing 3430, which includes lower battery cover 3432. Enclosedin the upper housing 3420 and lower housing 3430 are a motor 3460 andbatteries 3470, which can, optionally, be assembled into a battery pack.In the upper housing 3420 is a switch 3482 (which may be a momentaryswitch or an on-off switch) for providing power to the motor 3460 fromthe battery pack 3470. A flexible switch cover 3484 mounted in thesurface of the upper housing 3420 allows access to the power leveladjustment 3581 (FIG. 35A) inside. The upper housing 3420 furthercomprises a retractable blade hook control button 3499 (secured by acontrol button bolt 3498), as well as an instrument insertion tubesupport 3426 to orient the instrument insertion tube 3490 near andcoaxial with the motor 3460.

FIG. 35A shows an exploded view of Differential Dissecting Instrument3400. The Differential Dissecting Instrument 3400 is grossly comprisedof an instrument handle 3412 from which projects an instrument insertiontube 3490 which has a first end 3491 attached to instrument handle 3412and a second end 3493, to which is rotatably mounted a DDM 3492. Theinstrument handle 3412 is assembled from an upper housing 3420, whichincludes upper battery cover 3422, and a lower housing 3430, whichincludes a lower battery cover 3432, which are held together byinstrument housing bolts 3536. Included within the upper housing 3420and lower housing 3430 are a motor 3460 and batteries 3470, here shownas battery type CR123A (3V each, 18V for all 6 batteries 3470) but otherbattery types and voltages can be used. We've used batteries totaling aslow as 3V in some embodiments. In the upper housing 3420 is a switchport 3524, through which can be accessed switch 3482 (which may be amomentary switch or an on-off switch) for providing power to the motor3460 from the battery pack 3470. A printed circuit board 3580 furthercontaining a power level adjustment 3581 (which can be any convenientcomponent, but is here shown as a linear potentiometer) is provided andcan be accessed through a flexible switch cover 3484 mounted to thesurface of the upper housing 3420. Also included are forward springbattery connectors 3572 and aft spring battery connectors 3574, whichroute electric power from the batteries 3470. The upper housing 3420further contains an instrument insertion tube support 3426 to secure andorient the instrument insertion tube 3490 near and coaxial with themotor 3460. An instrument insertion tube retaining bolt 3527 holds theinstrument insertion tube 3490 securely in the instrument insertion tubesupport 3426.

The lower housing 3430 further provides access to and secures thebatteries 3470 with an integral lower battery cover 3432 and motorhousing section 3534, further held to the upper housing 3420 using thethree instrument housing bolts 3536. The motor housing section 3534holds and secures the motor 3460 coaxial with the instrument insertiontube 3490, which passes through the instrument insertion tube support3426. The motor 3460 is pressed forward by the motor housing section3534 against the motor spring 3562, the inside diameter of which leavesroom for the motor shaft coupler 3562. The motor shaft coupler 3562,with the help of the motor shaft coupler bolts 3566, mounts securelyonto the end of the shaft of the motor 3460 and further grips a firstend 3595 of a drive shaft 3494. The motor 3460 can slide longitudinallyfore and aft within the motor housing section 3534 under the control ofthe retractable blade hook control button 3499. The motor 3460 furthercomprises a power contact plate 3569 which operably slides againstsprung motor power contacts 3563 mounted on circuit board 3580. Alsomounted on circuit board 3580 is an adjustable power contact pressurecontrol bolt 3561. Normally, spring 3567 keeps motor 3460 aft. In thatposition, the sprung motor power contacts 3563 mounted on the printedcircuit board 3580 are aligned with and press against the power contactplate 3569 on motor 3460, and so electric power from battery pack 3470can drive motor rotation. Pressing the retractable blade hook controlbutton 3499 forward causes motor 3460 to slide forward. The powercontact plate 3569 is shorter than the full extent of travel of motor3460 under the influence of retractable blade hook control button 3499,such that electric power from battery pack 3470 is automatically cut offwhen the motor 3460 is slid sufficiently far forward toward insertiontube second end 3493 to break contact with sprung motor power contacts3563.

The drive shaft 3494 also has a second end 3597, which passes throughand is concentrically supported by a shaft bearing 3496 that is mountedonto the second end 3493 of instrument insertion tube 3490. Referringalso to FIG. 35 B, the second end 3597 of drive shaft 3494 furthercomprises (from the tip of second end of 3597 and working inward) a camreceiver retainer 3555, a cam receiver driver 3554, and a shaft bearingclearance section 3552. DDM 3492 is rotatably mounted onto shaft bearing3496 such that drive shaft 3494 causes DDM 3492 to rotate with areciprocal oscillation. DDM 3492, shaft bearing 3496, a cam receiver3596, a cam receiver retainer 3555, drive shaft 3494, and instrumentinsertion tube 3490 collectively form the DDM assembly 3598, which isdescribed next.

FIG. 35B depicts the details of DDM assembly 3598, including how DDM3492 is assembled with other components such that the motor 3460 drivesreciprocal oscillation of DDM 3492. DDM 3492 in this embodimentcomprises a tissue facing surface 3522 on a first end 3521 and a shaftbearing grip 3524 on a second end 3543. The shaft bearing grip 3524 isfurther fitted with two pivot pin holes 3525. The DDM 3492 may bepartially hollow, possessing a shaft bearing cavity 3526 that permitsthe shaft bearing 3496 to fit inside. The shaft bearing cavity 3526further sports a cam receiver cavity 3548 shaped to permit cam receiver3596 to easily slide therein. In this embodiment, tissue facing surface3522 of DDM 3492 further comprises a retractable blade slot 3506. Shaftbearing 3496 has a bore 3536, a shaft bearing tip 3532, a threadedbearing end 3538, and two insertable pivot pins 3535 that fit intothreaded holes 3534. The threaded shaft bearing end 3538 screws intothreaded shaft bearing mount 3542 on the second end 3493 of instrumentinsertion tube 3490. Bore 3536 can have a diameter greater than thediameter 3585 of drive shaft 3494 everywhere along its length, except atshaft bearing tip 3532, thereby decreasing the contact surface betweenshaft bearing 3496 and drive shaft 3494. Second end 3497 of drive shaft3494 is modified to include main shaft section 3552, cam shaft section3554, and cam receiver retainer 3555. Cam receiver 3596 furthercomprises a cam receiver body 3502, a cam receiver chamber 3505, and aretractable blade 3501. Retractable blade 3501 can further comprise ahook 3504 and a tissue engaging surface 3503. Tissue engaging surface3503 of retractable blade 3501 can be more or less aggressive thantissue engaging surface of DDM 3492. The various sub-components of thesecomponents allow for their assembly and operation, as is disclosedelsewhere in this document.

DDM 3492 fits over shaft bearing 3496, which is screwed into threadedshaft bearing mount 3542 of the instrument insertion tube 3490, all ofwhich coaxially encompass drive shaft 3494. It is notable that pivot pinholes 3525 on shaft bearing grip 3524 fit onto pivot pins 3535 of shaftbearing 3496. This arrangement, combined with shaft bearing cavity 3526,allows DDM 3492 to rotate freely on the pivot pins 3535. Rotation ofdrive shaft 3494 causes cam shaft section 3554 to rotate inside camreceiver 3596, driving DDM 3492 to reciprocally oscillate about thepivot pin holes 3525 and sweeping tissue facing surface 3522side-to-side. Tissue facing surface 3522 may possess a tissue-engagingsurface (not depicted here) such that it performs as a DDM.

In operation, a surgeon holds the differential dissecting instrument3400 by the instrument handle 3412 and orients the distal tip sportingthe DDM 3492 toward the complex tissue to be dissected. The surgeonselects the power level by sliding the power level adjustment 3581 tothe desired setting and then places his or her thumb upon the switch3482 and presses it to close the switch. When switch 3482 closes, motor3460 is turned on and rotates the motor shaft coupler 3562 and, in turn,the drive shaft 3494. The drive shaft 3494 is held coaxially and quiteprecisely in place by the shaft bearing 3496 and especially the shaftbearing tip 3532, so that the cam shaft section 3554 of the drive shaft3494 oscillates rotationally inside the cam receiver chamber 3505 of camreceiver 3502 captured within the DDM 3492. The rotational oscillationof the cam shaft section 3554 impinges on the walls of the cam receiverchamber 3505 of cam receiver 3502 which is configured as a scotch yokeas described earlier, forcing the entire DDM 3492 to rotate through anoscillation arc lying in a plane perpendicular to the axis of therotational joint formed by the pivot pins 3535 and the pivot pin holes3525. The surgeon can extend retractable blade 3501 by pushingretractable blade hook control button 3499 forward. Forward motion ofretractable blade hook control button 3499 causes motor 3460 and powercontact plate 3569 to move forward, separating power contact plate 3569from sprung motor power contacts 3563 and cutting power to the motor, asdescribed earlier, and preventing oscillation of DDM 3492.Simultaneously, forward motion of motor 3460 pushes drive shaft 3494forward, toward second end 3493 of instrument insertion tube 3490.Forward motion of drive shaft 3494 in turn pushes cam receiver retainer3555 against the top of cam receiver chamber 3505 inside cam receiverbody 3502, thereby pushing cam receiver body 3502 further up camreceiver cavity 3548 and extending retractable blade 3501 out ofretractable blade slot 3506. Thus, forward motion of retractable bladehook control button 3499 causes the motor 3460 to stop and retractableblade 3501 to extend out of DDM 3492. When retractable blade hookcontrol button 3499 is released, motor spring 3562 pushes motor 3460aft, retracting retractable blade 3501 and restoring electrical contactsfor the motor.

In this embodiment the amplitude of the oscillation through which thetissue facing surface 3522 of the differential dissecting member 3492swings is a function of the diameter 3585 of the drive shaft 3494 out ofwhich the cam shaft section 3554 is cut and the distance 3579 separatingtissue facing surface 3522 and pivot pin holes 3525. The frequency ofthe reciprocal oscillation (cycles per minute) of the DDM 3492 againstthe complex tissue matches the frequency of rotation (rotations perminute) of the motor 3460. The operator may control the oscillationfrequency of the tissue facing surface 3342 by varying the position ofthe power level adjustment 3581. Note that this mechanism for convertingrotation of motor 3460 and thus rotation of drive shaft 3494 intooscillation of the DDM 3492 is similar to the scotch yoke depicted inFIGS. 22 through 25C.

FIGS. 35C-1 and 35C-2 illustrate that fore/aft motion of drive shaft3494 and, thus of cam receiver body 3502, also alters the amplitude ofreciprocal oscillation of DDM 3492. Drive shaft 3494 is depicted in theaft position (having moved in the direction of arrow 3595) in FIG. 35C-1and in the fore position (having moved in the direction of arrow 3597)in FIG. 35C-2. Thus, as cam receiver body 3502 moves forward inside camreceiver cavity 3548, the distance D from cam receiver body 3548 andpivot pin holes 3525 increases to D′ while the lateral displacement ofthe receiver 3599 remains constant (because it is determined by thediameter 3585 of drive shaft 3494, as described above). As D′ increases,the larger angular amplitude of DDM 3596 in the left frame decreases tothe smaller angular amplitude of DDM 3492 in the right frame. Thiseffect can be used to decrease the amplitude of oscillation when aretractable blade is extended. It can also be used to alter theamplitude of oscillation during blunt dissection by the DDM, for examplewhen a surgeon wants a narrower oscillation for more precise dissection.

FIGS. 36A-1, 36A-2, 36B-1, 36B-2, 36B-3, and 36B-4 show the end of aDifferential Dissecting Instrument 3600 having a DDM 3610 rotatablymounted to instrument insertion tube 3620 via rotational joint 3630.Differential Dissecting Instrument 3600 also has a retractable hook 3640that can be extended or retracted by motion in the direction indicatedby double headed arrow 3650. Retractable hook 3640 can be retracted orextended using, for example, the mechanism described in FIGS. 34, 35A,and 35B. FIG. 36A demonstrates how retractable hook 3640 can be placedinto two configurations. CONFIGURATION 1 (FIG. 36A-1) shows retractablehook 3640 in the extended position, and CONFIGURATION 2 1 (FIG. 36A-2)shows retractable hook 3640 in the retracted position. Retractable hook3640 can have a tip 3670 that can be pointed or rounded and a tissueengaging surface 3660 that can be more aggressive than tissue engagingsurface 3690 of DDM 3610, or it can be less aggressive. Retractable hook3640 possesses an elbow 3680 that can be sharpened to slice, as shownhere, or it can be dull; furthermore, it can be serrated, and thesharpened region can be located anywhere within the elbow. InCONFIGURATION 2, retractable hook is hidden inside DDM 3610, and DDM3610 alone interacts with the tissue. In CONFIGURATION 1, retractablehook 3640 is exposed and can be used to interact with the tissue suchthat tissue engaging surface 3690 interacts with the tissue (e.g. todisrupt softer tissues), or such that tip 3670 interacts with tissue(e.g. to pierce a tissue), or elbow 3680 interacts with tissue (e.g. toslice a tissue), depending on how an operator positions retractable hook3640 with respect to the tissue. Additionally, retractable hook 3640 canbe held at any intermediate position between CONFIGURATION 1 andCONFIGURATION 2, including being able to be variably extended by anoperator.

FIGS. 36B-1 through 36B-4 show the end of a Differential DissectingInstrument 3600 and illustrates that DDM 3610 can oscillate withretractable hook in the extended configuration (CONFIGURATION 1) 1 (FIG.36B-1) or the retracted configuration (CONFIGURATION 2) 1 (FIG. 36B-2)and that retractable hook 3640 can be retracted or extended beforeactivation of oscillation of DDM 3610 or during oscillation of DDM 3610.Arrow 3601 shows retractable hook moving between the retractedconfiguration (lower left frame) to the extended configuration (upperleft frame—FIG. 36B-3) while DDM 3610 is not oscillating. Arrow 3602shows that DDM 3610 can be switched from stationary (upper left frame)to oscillating (upper right frame—FIG. 36B-4) while retractable hook3640 is in the extended configuration. Arrow 3603 shows that retractablehook 3640 can be moved from the extended configuration (upper rightframe) to the retracted configuration (lower right frame) while DDM 3610is oscillating. Arrow 3604 shows that DDM 3610 can change fromstationary (lower left frame) to oscillating (lower right frame) whileretractable hook 3640 is in the retracted configuration. Retractablehook 3640 can optionally be made of an electrically conductive material,like stainless steel, and electrically connected to an external surgicalelectrosurgical generator to allow retractable hook 3640 to act as anelectrosurgical hook.

Many tissues to be dissected are wrapped in a membrane or capsule that asurgeon must divide to gain access to that tissue. Once that membrane orcapsule has been divided, the surgeon proceeds with dissection throughthat tissue. FIGS. 37-1 through 37-4 illustrate in four panels a methodby which a Differential Dissecting Instrument 3600 can be used to safelyand quickly divide a membrane 3710 overlying a tissue 3700, such as theperitoneum overlying the gall bladder or the capsule surrounding aliver. In the upper left panel (FIG. 37-1), the Differential DissectingInstrument is seen approaching membrane 3710 with the retractable hook3640 in the extended configuration. In the upper right panel (FIG.37-2), the tissue engaging surface 3660 of retractable hook 3640 ispressed by the surgeon against membrane 3710, and the DDM 3610 isoscillated such that tissue engaging surface 3660 abrades membrane 3710.(Alternatively, the retractable hook 3640 can be held in the retractedconfiguration, and the tissue engaging surface 3690 of DDM 3610 can beused to abrade membrane 3710. If the two tissue engaging surfaces 3660and 3690 have different levels of aggressiveness, the surgeon then hasthe flexibility of choosing either the more aggressive or the lessaggressive tissue engaging surface to abrade the membrane 3710.) Thetissue is abraded until a small opening 3720 is made in membrane 3710.Next, as shown in the lower left panel (FIG. 37-3), the surgeon thenpries the tip 3670 of retractable hook 3640 through opening 3720 andunder membrane 3710, lifting or “tenting” a flap 3730 of membrane 3710away from tissue 3700. The surgeon then moves DDM 3600 in the directionof arrow 3740, thereby forcing flap 3730 into the elbow 3680 ofretractable hook 3640, the elbow 3680 being sharpened to slice tissue.Finally, as shown in the lower right panel (FIG. 37-4), the surgeonmakes DDM 3610 oscillate, causing retractable hook 3640 to oscillateand, thus, the sharp edge of the elbow 3680 of retractable hook 3640 toquickly move into membrane 3710 as the surgeon continues moving DDM 3600in the direction of arrow 3740. This has been demonstrated with freshtissues to be an easy, quick, and safe way to divide a membrane, such asthe peritoneum overlying the gall bladder and bile duct, withoutdamaging underlying structures (e.g. the gall bladder, bile duct, orliver). The tip 3680 of retractable hook 3640 can be made sufficientlyblunt that it does not easily penetrate the membrane 3710 or underlyingstructures; furthermore, the placement of the sharp edge only at elbow3680 prevents critical structures from being exposed to the sharp edge3680 and thus reducing the likelihood of such critical structures beingcut. Examples of membranes or capsules overlying critical structuresinclude the peritoneum overlying the liver, gall bladder, cystic duct,and cystic artery; and the pleura overlying the lung, pulmonary artery,pulmonary vein, and bronchus.

A retractable hook can be used in a method similar to that shown inFIGS. 37-1 through 37-4 to dissect tougher fibrous structures, likeadhesions, fibrous tissues surrounding the renal artery or vein, andscar tissue. For example, a surgeon can use the tip of a retractablehook to grab all or a portion of a fibrous structure and then can pushthe tissue into the sharpened elbow of the hook. The surgeon can thenoscillate the DDM and hook to use the sharp edge inside the hook to cutthe tissue. An advantage of this approach is that it applies thestresses in the immediate location of the tissue to be divided. Incurrent practice, surgeons divide such tissues by a variety oftechniques, including simply grabbing the sides or ends of such tissuesand pulling them until they break. This can at times put large stresseson the tissues being pulled, such as the wall of the intestine, leadingto accidental tearing of critical tissues, such as the wall of theintestine (and thereby perforating the bowel). By applying the stressesmore locally and directly to the tissue to be divided (specifically atthe sharpened elbow of the hook), and not over larger expanses oftissues (e.g. between two pairs of forceps), a surgeon can have greatercertainty that a more distant tissue, like the wall of the intestine, isunharmed.

It is important to note that these methods of dividing tissues by usinga hook that is oscillated does not heat the tissues, in stark contrastto the extreme heat that arises from current practice usingelectrosurgery. The heat from electrosurgery is widely acknowledged as amajor risk leading to accidental thermal damage of surrounding tissues.Competing technologies for sharp dissection, such as ultrasonic ablation(e.g. the “harmonic shears” from Ethicon Endosurgery), have beendeveloped to reduce the heat and thereby decrease the risk of thermaldamage to tissues. Nevertheless, local heating remains significant andthe risk of thermal damage is still present. On the contrary, dividing amembrane or dissecting a fibrous structure as described here with anoscillating hook causes no heating of tissues, eliminating this majorsource of iatrogenic trauma.

FIG. 38 shows one embodiment of a Differential Dissecting Instrument3800 for laparoscopic surgery. It uses the mechanism for oscillation ofthe DDM 3810 shown in FIGS. 34, 35A and 35B, including a retractableblade (not visible in this picture because it is in the retractedconfiguration). Differential Dissecting Instrument 3800 uses apistol-style handle 3820 having a trigger 3830 to start/stop oscillationof the DDM 3810 and a speed control 3840 for controlling the speed ofoscillation. A thumb-activated push-button 3850 is used to extend theretractable blade which is held in a normally retracted configuration bya spring mechanism inside handle 3820. A rotational wheel 3860 can bereached and turned with an index finger, and rotation of rotationalwheel 3860 rotates instrument insertion tube 3870 and attached DDM 3810such that the plane of oscillation 3880 of DDM 3810 can be easily turnedthrough 360 degrees, thereby allowing a surgeon to orient the plane ofoscillation 3880 with a tissue plane inside the body while maintaininggood ergonomics for the handle 3820. An indicator 3862 on rotationalwheel 3860 provides the surgeon with a visual cue outside the body as tothe orientation of the plane of oscillation 3880, and, similarly, visualcues, such as embossed stripes, can be placed on the instrumentinsertion tube 3870 or on DDM 3810 thereby providing a visual cue oncamera during laparoscopic viewing. An electrical plug 3890 allowsoptional attachment via cable to an external electrosurgical generatorfor electrosurgery and electrocautery (controlled by external footpedals attached to the electrosurgical generator for control of theelectrosurgical generator or, alternatively, push buttons (not shown)can be placed onto handle 3820 and used for control of theelectrosurgical generator). Differential Dissecting Instrument 3800,therefore, allows a surgeon to perform blunt dissection (viadifferential dissection), sharp dissection (via retractable hook orelectrosurgery), and coagulation (via electrocautery) with a singleinstrument, thereby reducing instrument changes which is complicated forlaparoscopic surgery.

FIG. 39 shows a Differential Dissecting Instrument 3900 configured as atool to be attached to the arm of a surgical robot, such as the da VinciRobot from Intuitive Surgical, Inc. DDM 3610 is rotatably attached toinstrument insertion tube 3910 via rotational joint 3630. Retractablehook 3640 can move between retracted and extended configurations, asindicated by double headed arrow 3650. Retractable hook 3640 has atissue engaging surface 3660, tip 3670, and elbow 3680 with a sharpenededge for sharp dissection. Retractable hook 3640 can, optionally, beelectrically conductive and electrically connected to an externalelectrosurgical generator. Similarly, DDM 3610 or a small electricallyconductive patch 3625 on DDM 3610 can be used for electrocautery. (Notethat an electrically conductive patch can be placed anywhere on DDM3610, including the tissue engaging surface 3690.) Instrument insertiontube 3910 attaches to housing 3920 which contains a motor to driveoscillation of DDM 3610 and retractable hook 3640 as described earlier.Housing 3920 is configured with socket 3930 having electrical andmechanical connections for connecting to the surgical robot's arm.Instrument insertion tube 3910 can be made long, such that housing 3920is located outside the patient's body. Conversely, instrument insertiontube 3910 can be made short, such that housing 3920 is located insidethe body, with articulations located in the robot arm and inside thepatient's body to permit articulated motion of Differential DissectingInstrument 3900 inside the patient's body.

Placement of a small motor in a housing closer to a DDM and inside thepatient's body facilitates articulation of the instrument insertion tubeof a Differential Dissecting Instrument because all connections from thehousing to the handle or housing, and thus through the articulation, canbe electrical, which can be much simpler than designs requiring thetransmission of mechanical drives through an articulation. This is truefor Differential Dissecting Instruments designed both for surgicalrobots and for laparoscopy.

FIGS. 40-1 and 40-2 show one embodiment of such a device as the end of alaparoscopic Differential Dissecting Instrument 4000. FIGS. 40-1 and40-2 show an exemplary laparoscopic version of a differential dissectinginstrument having electromechanical actuators distal to an articulation,and in the straight and bent positions, respectively. A DDM 3610 isfitted with a retractable hook 3640 and electrically conducting patch3625. DDM 3610 is rotatably attached to distal instrument insertion tube4010 which is articulated at rotational joint 4030 to proximalinstrument insertion tube 4020. Mounted inside distal instrumentinsertion tube 4010 are a motor 4040 with motor shaft 4050 and asolenoid 4060 with solenoid plunger 4070. Rotation of motor shaft 4050by motor 4040 drives oscillation of DDM 4010 and, thus, retractable hook3640, as described earlier. Solenoid 4060 is rigidly attached to distalinstrument insertion tube 4010, and solenoid plunger 4070 is attached tomotor 4040, which is free to slide inside distal insertion tube 4010.Thus, when solenoid 4060 is activated, solenoid plunger moves up/down(in the direction indicated by arrow 4080) thereby driving motor 4040,motor shaft 4050, and retractable hook 3640 up/down (as indicated byarrows 4080). Flexible conductor ribbon 4090 supplies the necessaryelectrical power and signals to drive motor 4040 and solenoid 4060.Articulation of laparoscopic Differential Dissecting Instrument 4000 atrotational joint 4030 allows distal instrument insertion tube 4010 tobend with respect to proximal instrument insertion tube 4020, as shownin the right hand panel. Motion of distal instrument insertion tube 4010with respect to proximal instrument insertion tube 4020 can be driven byany of several mechanisms, such as a control horn driven by a push-pullrod actuated by a hand-powered mechanism in the handle of thelaparoscopic Differential Dissecting Instrument 4000. This configurationof actuators (i.e. motor 4040 and solenoid 4060) and flexible conductorribbon 4090 facilitates the transmission of complex actions pastarticulation at rotational joint 4030, transmission that would otherwiserequire complex mechanical parts that are expensive, add bulk, and areprone to failure.

FIG. 41 shows a Differential Dissecting Instrument 4100 possessing athin, flexible instrument insertion tube 4110 for use in surgicalprocedures like single-incision laparoscopic surgery (SILS) or naturalorifice transluminal endoscopic surgery (NOTES). The actuationmechanisms are similar to the DDM 3492 and retractable hook 3596 inFIGS. 35A and 35B are identical to that shown in FIGS. 35A and 35B;however, the rigid instrument insertion tube 3490 and rigid drive shaft3494 are replaced by flexible instrument insertion tube 4110 andflexible drive shaft 4120, and the retractable hook 3596 is replacedwith an electrosurgical hook 4130. Flexible drive shaft 4120 can rotate(as shown by double-headed arrow 4160) to drive the oscillation of theDDM 3492 or it can push-pull (as shown by double-headed arrow 4162) toretract and extend the electrosurgical hook 4130. A multi-lumen flexibleinstrument insertion tube 4110 can be used to reduce wander of flexibledrive shaft 4120 inside the flexible instrument insertion tube, therebyproviding greater authority to the push-pull mechanism of the flexibledrive shaft 4120 for extending and retracting a electrosurgical hook4130. A flexible wire 4140 can also travel inside flexible insertiontube 4110 to allow conduction of electricity to electrosurgical hook4130, with flexible wire 4140 and electrosurgical hook 4130 beingconnected via a solder weld 4150 or other appropriate mechanism to camreceiver body 3502. Thus, the Differential Dissecting Instrument 4100 iscapable of blunt dissection, electrosurgical sharp dissection, andelectrocautery with controls located on a handset outside the body or,for electrosurgery or electrocautery, via foot pedals.

FIGS. 42A through 42E show oblique and expanded views of one embodimentof a Differential Dissecting Instrument 4200 that has a slender, pencilgrip handle that can be easily rotated in the hand, enabling 360°rotation of the plane of rotation of the DDM 4250 about the central,longitudinal axis 4299 of Differential Dissecting Instrument 4200.

FIGS. 42A and 42B show Differential Dissecting Instrument 4200 inoblique view, assembled in FIG. 42A and expanded in FIG. 42B.Differential Dissecting Instrument 4200 has an approximately cylindricalhandle 4210 possessing a longitudinal, central axis 4299. In use, adistal end 4201 of the handle 4210 is directed toward a tissue to bedissected, and a proximal end 4202 is pointed away from the complextissue and toward the user. Attached to the distal end 4201 is anelongate member 4220 parallel to the longitudinal axis 4299, having aproximal end 4222 attached to the distal end 4201 of the handle 4210 anda distal end 4221 pointing toward the tissue to be dissected. DDM 4250attaches to the distal end 4221 of the elongate member 4220. In thisembodiment, cylindrical handle 4210 is hollow, with a clamshellconstruction, such that it houses a mechanism 4260 configured tomechanically rotate the DDM 4250, as described in the next paragraph.

Referring now to FIGS. 42B, 42D, and 42E, FIG. 42B presents an expandedview of the Differential Dissecting Instrument 4200; FIG. 42D shows acloser view of the drive mechanism of the DDM 4250; and FIG. 42E shows asimplified view of the drive mechanism with emphasis on how the DDM 4250is driven. DDM 4250 is rotatably attached to the distal end 4221 of theelongate member 4220 such that DDM 4250 rotates about an axis ofrotation 4252. DDM 4250 possesses a first tissue engaging surface 4251at the distal end 4221 of DDM 4250, such that it is directed toward thetissue to be dissected, and a first torque-point 4253 disposed to afirst side 4255 of the axis of rotation 4252 of the DDM 4250 (see FIG.42E). Application of a first force 4270 to first torque-point 4253creates a moment on DDM 4250 about axis of rotation 4252 and thus drivesclockwise rotation of DDM 4250 about axis of rotation 4252. In theembodiment presented here, there is a second torque-point 4254 disposedto a second side 4256 of the axis of rotation 4252, whereby applicationof a second force 4271 drives counterclockwise rotation of DDM 4250.Thus the moment created by application of first force 4270 at firsttorque-point 4253 creates a counter-torque to second force 4271 atsecond torque point 4254. Alternating application of first force 4270and then second force 4271 thereby drives oscillation (clockwise thencounterclockwise) of DDM 4250 about axis of rotation 4252. Note thatfirst force transmitting member 4261 and second force transmittingmember 4262 can be a flexible tension member, such as a cable, wire,string, rope, tape, belt, or chain, or a rigid member, such as a pushrod or connecting rod. In the embodiment presented here, the first forcetransmitting member 4261 and the second for transmitting member 4264 areflexible tension members, such as cables.

Oscillation is driven by a motive source 4290 that is powered by a motor4291. Thus, motive source 4290 drives at least one force-transmittingmember 4261 axially, with respect to longitudinal axis 4299, proximallyand distally, thereby driving first torque-point 4253 of DDM 4250 aroundaxis of rotation 4252 and thereby making DDM 4250 oscillate around itsaxis of rotation 4252 such that the at least one tissue engaging surface4251 is configured to selectively engage the tissue to be dissected andsuch that the at least one tissue engaging surface 4251 moves across thetissue to be dissected whereby the at least one tissue engaging surface4251 disrupts at least one soft tissue in the tissue to be dissected,but does not disrupt firm tissue in the tissue to be dissected.

Referring now to FIGS. 42B, 42D, and 42E, mechanism 4260 drives therotation of DDM 4250. Mechanism 4260 (see especially FIG. 42D) comprisesat least one force-transmitting member 4261 that drives oscillation ofDDM 4250, as described in the preceding paragraph. As seen in FIGS. 42B,42D, and 42E first force-transmitting member 4261 and secondforce-transmitting member 4262 extend approximately parallel tolongitudinal axis 4299 inside elongate member 4220, and distal end 4264of first force-transmitting member 4261 attaches to first torque-point4253 of DDM 4250, and distal end 4266 of second force-transmittingmember 4262 attaches to second torque-point 4254 of DDM 4250. As seen inFIGS. 42B and 42D, proximal end 4263 of first force-transmitting member4261 attaches to a first follower 4231 of a cam shaft 4230, and proximalend 4265 of second force-transmitting member 4262 attaches to a secondfollower 4232 of cam shaft 4230. First follower 4231 rides on a firsteccentric cam 4233 (see inset) on cam shaft 4230, and second follower4232 rides on a second eccentric cam 4234 (see inset) on cam shaft 4230.Cam shaft 4230 rotates about an axis of rotation 4235 that isperpendicular to longitudinal axis 4299, and first eccentric cam 4233and second eccentric cam 4234 are positioned on opposite sides of axisof rotation 4235 such that first follower 4231 moves 180° out of phasewith respect to second follower 4232 (see FIGS. 42D and 42E for moredetail). Thus, rotation of cam shaft 4230 pulls alternately on firstforce-transmitting member 4261 and second force-transmitting member4262, creating the alternating first and second forces 4270 and 4271,respectively, that drives oscillation of DDM 4250, as described above.

Rotation of cam shaft 4230 is driven by motor 4291 via a gear train. Inthe embodiment presented here, motor 4291 is a DC electric motor formingpart of an electric circuit 4292 (see FIG. 42B) powered by at least onebattery 4294, whereupon the device further includes at least one switch4296 operatively associated with the motor 4291 and the at least onebattery 4294 to at least start and stop the motor 4291. Further controlscan be added to permit proportional speed control of motor 4291 or speedcontrol via incremental steps. Motor 4291 can be one of several types ofmotors, including brushless DC motors, coreless DC motors, steppermotors, etc.

Spring mechanism 4280, compression spring 4281, compression nut 4282,lock nut 4283, inner sleeve 4284, outer sleeve 4286, and spring stop4285 are described more completely after FIGS. 44A-1 through 44C-2below.

In the embodiment shown in FIGS. 42A through 42C, switch 4296 is part ofan omnidirectional control switch 4298 that makes the on-off switch formotor 4291 accessible from substantially any direction about thelongitudinal axis 4299 of handle 4210 of Differential DissectingInstrument 4200. In this embodiment, omnidirectional control switch 4298is comprised of five (5) switches 4296 in a radial array distributedabout the handle 4210, proximal to distal end 4201 of handle 4210, suchthat a switch 4296 can be easily activated with any finger regardless ofthe rotational orientation (about longitudinal axis 4299) ofDifferential Dissecting Instrument 4200 while in the user's hand. Inthis embodiment, the radial array of five switches 4296 is covered by aflexible boot 4297 made of a soft elastomer (e.g. silicone rubber) thatprevents intrusion of fluids into switches 4296 but still permits easyactuation of switches 4296. The switches can be either momentary orlatching. There may be any number of switches that form the radialarray; they may lie in a single plane oriented transverse to thelongitudinal axis 4299, or they may not, in which case the array ofswitches may further be distributed both around and along thelongitudinal axis 4299 of the Differential Dissecting Instrument 4200.The array of switches may or may not be the same; each of the switches4296 may vary in size, shape, type, function (momentary, latchingon-off, normally on, normally off. single-pole single throw, single-poledouble throw, double-pole double throw, double-pole single throw, ordigital or analog proportional control), or distance from thelongitudinal axis 4299, or any combination. Further, instead of an arrayof switches, the omnidirectional control switch 4298 may besubstantially monolithic or of toroidal construction, and may becomprised of, for example, a first ring conductor held in abeyance fromcontact with second ring conductor, whereupon the surgeon may applypressure to this version of the omnidirectional control switch 4298 fromany direction, causing the first ring conductor to come into electriccontact with the second ring conductor. Either the first ring conductoror the second ring conductor or both can be either rigid or flexible.For example, if the second ring conductor forms a small diameter rigidring around the longitudinal axis 4299 of the Differential DissectingInstrument 4200, the second ring conductor might be a large diameterring elastically suspended out of contact and substantially coaxiallywith the first ring conductor. As one example, the surgeon's fingersmight displace a rigid second ring conductor off-center until itcontacts the first ring conductor, or, alternatively, the second ringconductor might flexibly deform until contact is established with thefirst ring conductor. The omnidirectional control switch 4298 might takethe form of a power switch directly controlling the flow of electricityto a motor 4291, or, the omnidirectional control switch 4298 mighttransduce surgeon finger inputs into changes in resistance, capacitance,or other parameters in order to drive a logic circuit that then controlsthe motor 4291.

FIGS. 43A through 43C show different embodiments for imparting a torqueand counter-torque on a DDM 4300. In FIG. 43A, first tension element4261 and second tension element 4262 are two halves of a single cable4302 wrapped around a drive cylinder 4310 attached to DDM 4300. Singlecable 4302 drives rotation of drive cylinder 4310 either by friction orby being physically attached to drive cylinder 4310. Single cable 4302has a first end 4311 and a second end 4312 with first end 4311 acting asthe proximal end of the first force-transmitting member and the secondend 4312 acting as the proximal end of the second force-transmittingmember. First and second forces 4270 and 4271, respectively, are createdby the motion of rocker arm 4320 that rocks about rocker pin 4323 whendriven by linkage 4340 which is acentrically or eccentrically attachedto drive pulley 4343 which rotates (as indicated by arrow 4344) due tomotor 4342.

Another embodiment is shown in FIG. 43B where a linear spring 4350attaches to second torque-point 4254 and a stationary anchor point 4351such that application of first force 4270 rotates DDM 4300 and therebystretches linear spring 4350 and the return force 4271 of linear spring4350 generates the counter-torque when first force 4270 decreases.Similarly the counter-torque can be generated by a torsion spring 4360,as depicted in FIG. 43C.

FIGS. 44A-1 through 44C-1 show different embodiments of mechanisms thatprotect both a differential dissecting instrument and a tissue beingdissected from excessive loading. FIGS. 44A-1 and 44A-2 illustrate twodifficulties for the construct and use of a Differential DissectingInstrument 4400 that uses tension members as a force-transmittingmember, with FIG. 44A-1 showing no external force being applied and FIG.44A-2 showing an external force being applied. DDM 4410 has a tissueengaging surface 4412 on its distal end and a rotational joint 4414 onits proximal end to rotatably connect to the distal end of an elongatemember 4430. A first tension member 4421 connects to a firsttorque-point 4423, and a second tension member 4422 connects to a secondtorque-point 4424 such that first tension member 4421 and second tensionmember 4422 create a counter-torque around rotational joint 4414 todrive oscillation of DDM 4410. Difficulty #1: For first tension member4421 and second tension member 4422 to effectively provide acounter-torque about rotational joint 4414, they must remain taut.However, poor fit of components, stretching of first tension member 4421or second tension member 4422, wear, or other “play” in the DifferentialDissecting Instrument 4400 will cause Differential Dissecting Instrument4400 to perform poorly or to fail. Difficulty #2: During dissection oftissue 4405, application of an external force F_(A) to the DDM 4410 canforce the Differential Dissecting Instrument 4400 into an extremeposition, creating excessive bending or wear of first tension member4421 at point 4441 inside elongate member 4430 or of second tensionmember 4422 at point 4442 inside of elongate member 4430 (or at otherpoints of contact between either first or second tension member 4421 or4422 and another component). More broadly, excessive forces applied tothe DDM of a Differential Dissecting Instrument can damage theDifferential Dissecting Instrument or the tissue under dissection. Thusa means of preventing damage to either the instrument or the tissuewould be helpful.

FIG. 44B illustrates an embodiment of a Differential DissectingInstrument 4401 that addresses these difficulties including means forpreventing damage due to an overload condition. Differential DissectingInstrument 4401 possesses two overload mechanisms, a first overloadmechanism 4477 that is responsive to a first threshold force F_(T1)applied to DDM 4410 and a second overload mechanism 4470 that isresponsive to a second threshold force F_(T2) applied to DDM 4410.During dissection of tissue 4405, if force F_(A) is applied to the DDM4410 that exceeds a first threshold force F_(T1), first overloadmechanism 4477 stops rotation of DDM 4410 to reduce the risk of damageto either Differential Dissecting Instrument 4401 or to the tissue 4405being dissected. For example, first overload mechanism 4477 can includea force sensor 4461 that measures the force F_(A) applied to DDM 4410.Examples of force sensor 4461 include load cells, strain gauges, andspring-loaded electrical contacts. In this example, overload mechanism4450 resides in the handle 4411 where elongate member 4413 attaches tohandle 4411 but could be placed elsewhere, for example inside elongatemember 4413. Force sensor 4461 is in communication via wire 4462 withelectric circuit 4292, and when F_(T1) exceeds F_(A) a signal is sentvia wire 4462 to electric circuit 4292 which responds by cutting powerto motor 4290 thereby stopping oscillation of DDM 4410. Alternate meansexist for stopping rotation of DDM 4410. For example, a clutch on motor4290 could limit torque being applied by motor 4290 such that whenexternal force F_(A) is too large, the torque becomes too great and theclutch slips, or the motor 4290 could simply be sufficiently small thatit stalls, etc.

If force F_(A) is applied to DDM 4410 that exceeds a second thresholdforce F_(T2), second overload mechanism 4470 withdraws DDM 4410proximally away (in the direction of arrow 4471) from the tissue 4405thereby reducing external force F_(A). Note that first overloadmechanism 4477 and second overload mechanism 4470 can be activated inresponse to any force, not just an axial force, as shown in FIG. 44B.Furthermore, first threshold force F_(T1) can be equal to, greater than,or less than second threshold force F_(T2), depending on the desiredresponse. Also note that a Differential Dissecting Instrument can befitted with only one of the two overload mechanisms 4470 and 4477.

FIGS. 44C-1 and 44C-2 illustrate a different embodiment of aDifferential Dissecting Instrument 4402 with a single overload mechanismas described above for FIG. 44B, with FIG. 44C-1 showing no externalforce being applied and FIG. 44C-2 showing an external force beingapplied. Differential Dissecting Instrument 4402 is similar toDifferential Dissecting Instrument 4401, however, now elongate member4430 is replaced by another exemplary overload mechanism 4450 which actsin the same way as second overload mechanism 4470 described above, bywithdrawing DDM 4410 proximally away from tissue 4405. Overloadmechanism 4450 comprises an outer sleeve 4451 with a first spring stop4454, an inner sleeve 4452 with a second spring stop 4455, and acompression spring 4453. Outer sleeve 4451 and inner sleeve 4452 arealigned parallel to the longitudinal axis 4299 of the handle. DDM 4410is attached to inner sleeve 4452 at rotational joint 4414. Inner sleeve4452 is free to slide proximally inside outer sleeve 4451. As shown onthe left-hand side (with no external force applied) compression spring4453 causes inner sleeve 4452 to slide distally inside outer sleeve 4451due to compression force 4460 being applied to first spring stop 4454and second spring stop 4455. Sliding is limited by forces 4462 and 4463exerted by first and second tension members 4421 and 4422, respectively,such that the combined force of force 4462 and force 4463 equalscompression force 4460. Thus, overload mechanism 4450 fixes Difficulty#1 described above in that compression spring will adjust the positionof inner sleeve 4452 relative to outer sleeve 4451 whenever any playaccumulates, such as stretching of first and second tension members 4421and 4422, respectively. The right-hand side of FIG. 44B shows howoverload mechanism 4450 also alleviates the problems of Difficulty #2.When an external force F_(A) is applied to DDM 4410, a moment is createdabout rotational joint 4414 forcing DDM 4410 into an extreme positionand also applies a moment at torque-point 4424 that stretches secondtension member 4422, creating a larger force 4463 on second tensionmember 4422. The increase in force 4463 thereby increases thecompression force 4460 on compression spring 4453. In response,compression spring 4453 compresses allowing inner sleeve 4452 to slideproximally (arrow 4456) inside outer sleeve 4451 and thus shortenoverload mechanism 4450. This withdraws DDM 4410 proximally away fromthe tissue being dissected thereby decreasing the magnitude of force4463 on second tension member 4422 and reducing the risk of damage toDifferential Dissecting Instrument 4402, and especially to secondtension member 4422. Note that other embodiments for withdrawing a DDMin response to an overload are possible. Different configurations ofsprings, flexible or bendable elongate members, friction pads that slipon overload, etc. are all possible.

Returning now to FIG. 42D, spring mechanism 4280 comprises compressionspring 4281, compression nut 4282, lock nut 4283, inner sleeve 4284, andspring stop 4285. Compression spring 4281 surrounds inner sleeve 4284and is compressed between compression nut 4282 (which serves as thefirst spring stop 482) and spring stop 4285 (which serves as the secondspring stop) such that it pulls on first tension element 4261 and secondtension element 4262. The strength with which compression spring 4282pulls is set by compression nut 4282 which is threaded onto inner sleeve4284—advancing compression nut 4282 downward (with respect to the page)compresses compression spring 4281, increasing the strength with whichcompression spring 4281 pulls on first tension element 4261 and secondtension element 4262. After an appropriate pull is established,compression nut 4283 can be locked with lock nut 4283. This means forvarying the strength with which compression spring pulls on firsttension element 4261 and second tension element 4262 effectively setsthe threshold force at which the compression spring 4281 is overcome byan external force, as discussed in FIG. 44B. Furthermore, the distanceof advance of compression nut 4283 along inner sleeve 4284 defines thedistance over which compression spring can remove slack from themechanism arising from, for example, stretch of first tension element4261 and second tension element 4262. The travel of inner sleeve

FIGS. 45A through 45G show a method for using a differential dissectinginstrument for separating a tissue plane without damaging blood vesselsand other anatomical structures in the tissue plane. FIGS. 45A through46G depict a method for using a Differential Dissecting Instrument 4530to dissect apart two tissues adjoining at a tissue plane. In FIG. 45A,first tissue 4501 and second tissue 4502 adhere at a common border 4504,with Soft Tissue 4505 acting as an adhesive between the first capsule4506 of first tissue 4501 and a second capsule 4507 of second tissue4502. In this example, one blood vessel 4520 (depicted in cross-section)lies in the plane of the common border 4504, in between the firstcapsule 4506 and the second capsule 4507; a second blood vessel is a“perforator” 4510 that crosses the common border 4504 going from tissue4501 to tissue 4502; and one collagenous bundle 4515 also crosses thecommon border 4504 going from first tissue 4501 to second tissue 4502.Thus, if first tissue 4501 is to be separated from second tissue 4502 byblunt dissection, then soft tissue 4505 must be disrupted, preferablywithout disrupting the perforator 4510, collagenous bundle 4515, orblood vessel 4520. (Disruption of the blood vessels can lead tounnecessary bleeding.) Again, 4505 is a Soft Tissue, typically comprisedof gelatinous materials, mesenteries, reticular fibers, and looselyorganized collagen fibrils. Firm Tissues include first and secondcapsules 4506 and 4507, respectively, the walls of blood vessels 4510and 4520, and collagenous bundle 4515.

Blunt dissection is performed by first grasping first tissue 4501 withforceps 4540 and pulling in the direction of arrow 4550 to apply tensionat the edge of common border 4504, as indicated by double-headed arrow4536. Application of tension across common border 4504 is importantthroughout this dissection as such tension assists the differentialaction of the Differential Dissecting Instrument 4530, as discussedabove. Differential Dissecting Instrument 4530 comprises a DDM 4532 withtissue engaging surface 4533, with DDM being rotatably mounted oninstrument insertion tube 4531 such that it oscillates into and out ofthe plane of the page (as indicated by rotational axis 4535), causingtissue engaging surface 4533 to swipe against the edge of common border4504. Force 4551 is applied by the operator to push tissue engagingsurface 4533 into the edge of common border 4504, thereby causingablation of Soft Tissue 4505 and ensuing separation of the first andsecond capsules 4506 and 4507 of the first and second tissues 4501 and4502, respectively, as shown in FIG. 45B. If the tissue engaging surface4533 wanders up or down due to inaccuracy of placement or misdirectionof force 4551 by the operator, the tissue engaging surface 4533 will notdisrupt and, therefore, will not cross either capsule 4506 or 4507.Thus, Differential Dissecting Instrument automatically follows the planebetween the tissues, defined by common border 4504.

In FIG. 45C, tissue engaging surface 4533 continues along common border4504 until it impinges on blood vessel 4520. Again, tissue engagingsurface 4533 will not disrupt the Firm Tissue comprising the wall ofblood vessel 4520. Instead, tissue engaging surface 4533 moves to oneside or the other of blood vessel 4520 (here seen moving below bloodvessel 4520), depending on whether Soft Tissue 4505 is more easilydisrupted above or below blood vessel 4520 or if the operator pushesDifferential Dissecting Instrument 4530 above or below the blood vessel4520. The operator knows to push Differential Dissecting Instrument 4530in a different direction because the operator can sense tissue engagingsurface 4533 impinging on blood vessel 4520 as an increase in resistanceto pushing Differential Dissecting Instrument 4530 into the commonborder 4504—progress of the Differential Dissecting Instrument 4530practically stops because the tissue engaging surface 4533 will notdisrupt and thus cross the Firm Tissue composing the wall of bloodvessel 4520.

Blunt dissection continues in FIG. 45D along common border 4504 as theoperator continues to apply tension 4536 across common border 4504 withforceps 4540 and to push Differential Dissecting Instrument 4530 intothe common border 4504. Capsules 4506 and 4507 continue channeling theDifferential Dissecting Instrument 4530 along common border 4504 bypreventing the tissue engaging surface 4533 from crossing either firstcapsule 4506 or second capsule 4507 until tissue engaging surface 4503impinges onto collagenous bundle 4515. Again, tissue engaging surface4533 cannot disrupt collagenous bundle 4515, and, again, the operatorsenses that further progress of Differential Dissecting Instrument 4530into the common border 4504 is blocked. The operator then works theDifferential Dissecting Instrument to one side or the other, which asseen in FIG. 45E is to the rear of collagenous bundle 4515 for thisexample, and then continues dissecting along common border 4504 untiltissue engaging surface 4533 impinges now on perforator 4510. Again, theoperator senses an obstruction and moves the Differential DissectingInstrument 4530 to one side or the other, which as seen in FIG. 45F isto the rear of perforator 4510 in this example.

FIG. 45G shows the resulting dissection after Differential DissectingInstrument 4530 has been removed. The common border 4504 has now beendissected such that the capsules 4506 and 4507 of tissues 4501 and 4502,respectively, are separated, providing a critical view for the surgeon.Importantly, blood vessel 4520 is unharmed; collagenous bundle 4515 isstretched in the gap between first capsule 4506 and second capsule 4507,and perforator 4510 is stretched across the gap between first capsule4506 and second capsule 4507. Collagenous bundle 4515 and perforator4520 are, thus, “skeletonized”, they are seen now in open space wherethey can be cauterized and cut without touching either the capsules 4506or 4507 or tissues 4501 or 4502. This is especially important ifbleeding from perforator 4510 is to be controlled when tissues 4501 and4502 are separated and, also, if contact with or thermal spread from theelectrocautery surface might cause thermal damage to either tissue 4501or 4502.

The dissection technique, such as that shown in FIGS. 45A through 45F,has been used by the inventors to perform several surgical dissections(in ex vivo animal tissues, live animal tissues (pig), and in humancadavers) such as, for example, to separate the gall bladder from thebed of the liver, to separate adjacent muscles, to separate a bloodvessel from a bladder or from another blood vessel, to separate adjacentlobes of the lung, to isolate the pulmonary artery and the cystic ductand cystic artery, and many others. Strikingly, each of thesedissections has been remarkably blood-free, owing to the DifferentialDissector's ability to dissect without disrupting either blood vessels,even blood vessels as small as 0.5 mm outer diameter, or tissuecapsules. Furthermore, the dissection has been remarkably safe. Duringthese surgeries the surgeon deliberately attempted maneuvers that wouldhave been catastrophic with another instrument. For example, the surgeonstabbed the liver repeatedly with the Differential Dissecting Instrumentset on high speed, and bounced the Differential Dissecting Instrument onthe pulmonary artery, and stabbed into the large bowel, urinary bladder,and lung—there was no damage to any organ. As described earlier, theabsence of sharp edges in a DDM allows it to perform blunt dissectionsafely, unlike any other surgical instrument.

A dissection with a Differential Dissecting Instrument, such as thatshown in FIGS. 45A through 45F can be used, for example, to dissectfascial planes during a tummy tuck procedure. In fact, it is possible todissect these tissue planes without cauterizing or cutting perforators.Rather, by working around perforators to skeletonize them duringdissection, using the Differential Dissecting Instruments shown herein,sufficient separation of tissue planes can be achieved to permitdissection to be advanced without having to cut perforators, which isusually done to avoid accidental tearing or to permit sufficientseparation of the tissues to permit viewing the dissection as itadvances. Preserving perforators, rather than cutting them, maintainsnormal blood flow to the superior layers which is otherwise compromisedby disruption of perforators. This result is truly remarkable and ofgreat clinical importance. Maintenance of normal blood flow lessens thechance of tissue necrosis (due to insufficient blood flow) and increasesthe chance for a rapid and complete recovery (due to sufficient bloodflow). This is extremely important whenever skin has been lifted fromunderlying tissues (e.g. for cosmetic or reconstructive procedures) orwhenever a flap of tissue is to be isolated but preserved.

A Differential Dissecting Instrument, such as any of those disclosedherein, can be used to dissect through fatty tissues; however, in such adissection through fat there are no organ capsules or other Firm Tissuesto guide the Differential Dissecting Instrument, and the dissectionproceeds solely under guidance of the operator, rather than being guidedby the bordering Firm Tissues. Such a dissection has been used toseparate the skin from underlying tissues for a face lift in a humancadaver. Importantly, as described above, a sufficient gap wasgenerated, without accidentally or intentionally disrupting perforatingblood vessels, to advance the dissection through to completion. In aliving patient, such a procedure would maintain normal blood flow to thetissues throughout the surgical procedure and, thus, into recovery. Thisis in stark contrast to the prior art which cauterizes perforation bloodvessels, cutting off this circulation and badly comprising normal bloodflow. As discussed above, preserving perforators, rather than cuttingthem, maintains normal blood flow to the skin which is otherwisecompromised by disruption of perforators. Maintenance of normal bloodflow lessens the chance of tissue necrosis (due to insufficient bloodflow) and increases the chance for a rapid and complete recovery (due tosufficient blood flow). Both are strongly desired outcomes of allsurgical procedures, but especially cosmetic surgical procedures.

A Differential Dissecting Instrument, such as any of those disclosedherein, can be used, in similar fashion, to tunnel into and through aportion of the body, allowing tissue capsules, blood vessel walls, nervebundles, and other Firm Tissues to guide the tissue engaging surfacealong existing tissue planes. For tunneling, however, the operator doesnot move the Differential Dissecting Instrument from side to side toseparate broad sections of tissue planes; rather, the operator pushesthe Differential Dissecting Instrument into the tissue plane, with onlylimited motion to the side, to create a narrow tunnel. Such tunnels areused in many surgical procedures, such as tunneling to position pacingleads for pacemakers and other heart rhythm management devices, and areincreasingly being used in minimally invasive surgical procedures, suchas robotic, thoracoscopic, and laparoscopic surgery, to reduce thedisruption of tissues, and thus trauma to tissues, during surgery. Oneproblem that arises in tunneling is lack of visibility at the terminalend of the tunnel—surgeons do not like to work blind.

FIGS. 46A-1, 46A-2, 46B-1, 46B-2, 46C-1, and 46C-2 show an instrumentfor tunneling with a differential dissecting instrument coupled with anendoscope. FIGS. 46A through 46C depict a dissection system 4600 fortunneling with a Differential Dissecting Instrument and with visibilitybeing provided by a television camera or other viewing device. As shownin FIGS. 46A-1 and 46A-2, dissection system 4600 is comprised of aninstrument tube 4610 having two lumens, endoscope lumen 4620 andinstrument lumen 4630. Additional lumens can be used to simultaneouslyintroduce multiple instruments.

As seen in FIGS. 46B-1 and 46B-2, endoscope lumen 4620 houses anendoscope 4640 that is fitted with a television camera or other viewingdevice at the opposite end (not shown), thereby providing a view of thedissection to the operator. Endoscope 4640 can also include fiberoptics,separate from those used for the camera, to deliver light into the fieldof dissection. Instrument lumen 4630 is used to insert one of severaldifferent instruments into the field of view of the camera whereby theyare used to dissect or otherwise manipulate tissue under view of theendoscope 4640. FIGS. 46B-1 and 46B-2 show instrument tube 4610 equippedwith an endoscope 4640 inside endoscope lumen 4620 and a DifferentialDissecting Instrument 4650 having a DDM 4655 inside instrument lumen4630. Endoscope 4640 has a field of view 4645 that permits viewing ofthe DDM 4655 of Differential Dissecting Instrument 4650 and itsinteraction with tissue. Differential Dissecting Instrument 4650 can berotated inside instrument lumen 4630 to permit the plane of oscillationof the DDM 4655 to be rotated to align with different tissue planes.(The plane of oscillation should be parallel to the tissue plane.)

Multiple instruments can be inserted, one at a time, into instrumentlumen 4630, as needed. FIGS. 46C-1 and 46C-2 show an electrosurgicalinstrument (e.g. a hook) 4660 inserted into instrument lumen 4630.Electrosurgical hook 4660 can also be inserted into and rotated insideinstrument lumen 4630 to allow the hook to point in any direction. Inuse, instrument tube 4610 is loaded with endoscope 4640 inside endoscopelumen 4620 and with Differential Dissecting Instrument 4650 loaded intoinstrument lumen 4630. The instrument tube is positioned by an operatorat the correct point on a patient, as determined by viewing the displayof endoscope 4640, who activates Differential Dissecting Instrument 4650to initiate blunt dissection. Differential Dissecting Instrument 4650can be rotated inside instrument lumen 4630, as indicated by curveddouble arrow 4657, to align the plane of oscillation with a tissueplane; furthermore, Differential Dissecting Instrument 4650 can beadvanced into and out of instrument lumen 4630, as indicated by straightdouble arrow 4656, such that DDM 4655 projects further or less from theface 4605 of instrument tube 4610, as needed for dissection. As thetunnel is opened, dissection system 4600 is advanced into the tunnel,with endoscope 4640 providing a view for the operator as the tunnel isopened up. If sharp dissection or electrocautery is needed, thenDifferential Dissecting Instrument 4650 can be removed andelectrosurgical hook 4660 can be introduced into instrument lumen 4630to cut or to cauterize.

Conversely, a Differential Dissecting Instrument having an extendableelectrosurgical hook, such as the Differential Dissecting Instrumentshown in FIG. 41, can be used to avoid having to switch back and forthbetween Differential Dissecting Instrument 4650 and electrosurgical hook4660. Other instruments, such as scissors, forceps, bipolar forceps, orultrasonic cutters, can also be introduced via instrument lumen 4630 asneeded for the dissection, or they can be part of a multi-functionDifferential Dissecting Instrument, as described earlier.

A dissection system such as dissection system 4600 can be used for manytypes of endoscopic tunneling, such as endoscopic saphenous veinharvesting, endoscopic tunneling for anterior access to the vertebralcolumn, for tunneling into the neck, for tunneling into the lung forlobectomy, or for tunneling to the heart for minimally invasive valvereplacement. A major advantage of dissection system 4600 over existingendoscopic saphenous vein harvesting systems is that addition ofdifferential dissection decreases the chance of side branch evulsion ordamage to the vessel wall. Normally, such trauma to the vessel requiressurgical repair, such as suturing evulsions, and is thought to greatlyimpair the quality of the graft during coronary artery bypass grafting,degrading the long-term durability of the graft.

In one demonstration of the effectiveness of a Differential DissectingInstrument, as disclosed herein, for safely dissecting a major vesselwith side grafts, a surgeon inserted a Differential DissectingInstrument into an incision over a vessel in a live pig (approximately120 lbs) and then blindly advanced the Differential DissectingInstrument along the path of least resistance, assuming this was thetissue plane overlying the vessel. At the conclusion of dissection alonga 20 cm path, the surgeon dissected down, to the shaft of theDifferential Dissecting Instrument, discovering that, yes, theDifferential Dissecting Instrument had followed the vessel and that thevessel had been freed from surrounding tissue with no evulsions of sidebranches or bruising of the main vessel wall.

FIGS. 47A through 47D show another instrument for tunneling with adifferential dissecting instrument coupled with an endoscope andincluding accessory components to enhance dissection and to improve thefield of view for the endoscope. FIG. 47A through 47D depict adissecting system 4700 like the dissecting system 4600 for tunnelinginto a tissue, such as along a blood vessel. However, the dissectingsystem 4700 includes:

-   -   an inflatable annular balloon 4710 located at the distal end of        the instrument tube 4610 that, on inflation, both expands the        diameter of the tunnel into the tissue 4701 and forms an        airtight seal between the instrument tube 4610 and the        surrounding tissue 4701 and    -   an insufflation system 4720 (a system that injects air to expand        a cavity inside the body) that permits both inflation/deflation        of the balloon 4710 and injection of pressurized air into the        end of the tunnel and thus into the tissue 4701 to expand the        end of the tunnel, assisting blunt dissection, and providing a        cavity 4702 distal to the face 4605 allowing the camera 4640 to        view the tissue 4701 and the action of instruments inserted into        the second instrument lumen 4630.

FIGS. 47A-1 and 47A-2 show front and side views, respectively, of thedistal end of the dissecting system 4700. As with the dissecting system4600, there is a multi-lumen instrument tube 4610 with an endoscope 4640inserted into the first instrument lumen 4620 and a DifferentialDissecting Instrument 4650 (or other instrument) inserted into thesecond instrument lumen 4630. The balloon 4710 wraps the end of theinstrument tube 4610 and can be inflated by air flow 4714 through aninflation tube 4712. The balloon 4710 is shown deflated in FIG. 47Awhereby it lies closely apposed to the instrument tube 4610 tofacilitate insertion of the instrument tube 4610 into the tissue 4701.

FIGS. 47B-1 and 47B-2 show front and side views, respectively, inflationof the balloon 4710 by an air flow 4714 which is provided by the ballooninflation tube 4712 and driven by air pumping device 4718 (shown in FIG.47D). Air pumping device 4718 can be on of any number of devices forproviding regulated air flows including syringes, air pumps, and such.Note that the airflow 4714 can be in the opposite direction as drawn,permitting deflation of the balloon 4710 when needed.

As shown in FIG. 47C, inflation of the balloon 4710 pushes the tissue4701 radially away from the distal end of the instrument tube 4610, asindicated by the arrows 4716. Thus the instrument tube 4610 can beinserted into a tissue 4701 with the balloon 4710 deflated. Afterinsertion, the balloon 4710 can be inflated to help create a cavity 4702and thereby improve the view for the camera 4740 attached to theendoscope 4640.

An insufflation system 4720 can also be attached to the proximal end ofthe instrument tube 4610 (see FIG. 47D). The insufflation system 4720comprises an insufflation tube 4726 that connects the second instrumentlumen 4630 to an air pump 4728 that provides a regulated air flow. Theregulated air flow is controllable by the operator such that air can beinjected into or withdrawn from the second instrument lumen 4630 viainsufflation tube 4726. Air pump 4728 can be one of any number ofdevices for providing regulated air flows, including syringes, airpumps, and such. Pressurized air flows into the insufflation tube 4726(as shown by the arrow 4724), into and along the second instrument lumen4630, and exits into the cavity 4702 at the distal end of the instrumenttube 4610 as shown by arrow 4724 in FIG. 47C. Air is blocked fromexiting the second instrument lumen 4630 by a seal 4722 between theDifferential Dissecting Instrument 4650 (or any other instrumentinserted into the second instrument lumen 4630) and second instrumentlumen 4630. Air inside the cavity 4702 can thus be pressurized whichfurther expands the cavity 4702 to improve visibility for the camera4740 attached to the endoscope 4640 and maneuverability for theDifferential Dissecting Instrument 4650. Pressurized air inside thecavity 4702 also tensions the tissues along the periphery of the cavity4702 including the region of dissection 4704 for the DDM 4655. (Asdescribed earlier, tensioning of the tissue facilitates differentialdissection; this can also be done by placing the differential dissectingmember inside the balloon, working on and dissecting the tissues throughthe balloon membrane, and letting the balloon expansion apply thetension normally supplied by other instruments.) The seal 3022 canoperate to block air flow both when an instrument, such as theDifferential Dissecting Instrument 4650 or the electrosurgical hook4660, is inserted into the second instrument lumen 4630. A second seal4723 can optionally be placed between the endoscope 4640 and the firstinstrument lumen 4620 to stop airflow out any gaps.

The embodiments set forth herein are examples and are not intended toencompass the entirety of the invention. Many modifications andembodiments of the inventions set forth herein will come to mind to oneskilled in the art to which these inventions pertain having the benefitof the teaching presented in the foregoing descriptions and theassociated drawings. Therefore, it is to be understood that theinventions are not to be limited to the specific embodiments disclosedand that modifications and other embodiments are intended to be includedwithin the scope of the appended claims. Although specific terms areused herein, they are used in a generic and descriptive sense only andnot for the purposes of limitation.

We claim:
 1. A differential dissecting instrument (DDI) fordifferentially dissecting complex tissue comprising: a handle, having acentral, longitudinal axis; a distal end of the instrument configured tobe pointed at a complex tissue, and a proximal end of the instrumentconfigured to be pointed at a user; an elongate member having a distalend and a proximal end, the proximal end of the elongate memberconnected to the handle; and a differential dissecting member rotatablyattached to the distal end of the elongate member, the differentialdissecting member having an axis of rotation and comprising: at leastone tissue-engaging surface; a first torque-point, the firsttorque-point disposed to a first side of the axis of rotation of thedifferential dissecting member; and a mechanism, configured tomechanically rotate the differential dissecting member around the axisof rotation thereby causing the at least one tissue-engaging surface tomove in at least one direction against the complex tissue, the mechanismcomprising: at least one force-transmitting member possessing a distalend and a proximal end, the distal end being attached to the firsttorque-point of the differential dissecting member; and the proximal endof the at least one force-transmitting member attached to a motivesource; and a second torque-point disposed to a second side of the axisof rotation of the differential dissecting member, providing acounter-torque on the differential dissecting member, wherein thecounter-torque is provided by a second force-transmitting membercomprising a distal end and a proximal end, the distal end beingattached to the second torque-point of the differential dissectingmember, forming an opposed pair of force-transmitting members, whereinfirst and second force-transmitting members of the opposed pair offorce-transmitting members each terminate on their respective proximalends in a respective cam follower on a cam shaft, and a cam follower ofthe first force-transmitting member and a cam follower of the secondforce-transmitting member both engage a single cam shaft; wherein the atleast one tissue-engaging surface is configured to selectively engagethe complex tissue such that when the differential dissecting member ispressed into the complex tissue, the at least one tissue-engagingsurface moves across the complex tissue and the at least onetissue-engaging surface disrupts at least one soft tissue in the complextissue, but does not disrupt firm tissue in the complex tissue, andwherein the differential dissecting member, and the mechanism configuredto mechanically rotate the differential dissecting member around theaxis of rotation that are distal from the cam shaft, form an outputshaft and tip assembly, and a compressed compression spring isconfigured to force the output shaft and the tip assembly toward thedistal end of the instrument, such that travel of the output shaft andthe tip assembly toward the distal end of the instrument is resisted andthus limited by tension in the opposed pair of force-transmittingmembers.
 2. A DDI as in claim 1, wherein the at least oneforce-transmitting member is a connecting rod.
 3. A DDI as in claim 1,wherein a rotation of the differential dissecting member imparted by theat least one force-transmitting member is counterbalanced by acounter-torque about the axis of rotation.
 4. A DDI as in claim 3,wherein the counter-torque about the axis of rotation of thedifferential dissecting member is supplied by a torsion springconfigured to resist the rotation imparted to the differentialdissecting member by the at least one force-transmitting member.
 5. ADDI as in claim 1, where the at least one force-transmitting member is atension member.
 6. A DDI as in claim 5, wherein a proximal end of thetension member terminates on a cam follower.
 7. A DDI as in claim 5,wherein the tension member is a cable.
 8. A DDI as in claim 5, whereinthe tension member is formed of a flexible tension member, such as awire, string, rope, tape, belt, or chain.
 9. A DDI as in claim 5,wherein the tension member comprises a single, continuous tensionmember, such as a loop.
 10. A DDI as in claim 9, wherein the single,continuous tension member has a first end and a second end, and wherethe first end of the single, continuous tension member forms theproximal end of the first force-transmitting member, and where thesecond end of the single, continuous tension member forms the proximalend of the second force-transmitting member.
 11. A DDI as in claim 1,wherein the motive source is a cam shaft driven by a motor.
 12. A DDI asin claim 1, wherein a spring is attached to the second torque-point ofthe differential dissecting member, wherein the spring is configured toresist the rotation imparted to the differential dissecting member bythe at least one force-transmitting member.
 13. A DDI as in claim 1,wherein the single cam shaft comprises a first eccentric cam configuredto engage the cam follower of the first force-transmitting member and asecond eccentric cam configured to engage the cam follower of the secondforce-transmitting member; and wherein the cam shaft possesses a centralaxis of rotation, and wherein the first eccentric cam and the secondeccentric cam are arranged about the central axis of rotation onehundred and eighty degrees from each other, such that when the cam shaftrotates, the cam follower of the first force-transmitting member is mostproximal while simultaneously the cam follower of the secondforce-transmitting member is most distal.
 14. A DDI as in claim 1,wherein the first and second force-transmitting members are flexibletension members.
 15. A DDI as in claim 1, wherein the motive source is alinear actuator.
 16. A DDI as in claim 1, wherein a force applied by thecompressed compression spring is adjustable to a level below that whichdamages tissue, such that a proximally directed force further compressesthe spring, driving the differential dissecting member assemblyproximally, thereby reducing the spring force on and so relaxing thetension members, whereupon the tension members lose tension, such thatthe differential dissecting member stops rotating even though the camshaft is still being rotated by the motive force, and so constitutes aforce overload safety factor.
 17. A DDI as in claim 1, furthercomprising at least a first overload mechanism configured to respond toa force applied in a proximal direction onto the differential dissectingmember such that when the force exceeds at least a first thresholdforce, the at least first overload mechanism stops rotation of thedifferential dissecting member.
 18. A DDI as in claim 1, furthercomprising an omnidirectional control switch, accessible fromsubstantially any direction about the long axis of the differentialdissecting instrument.
 19. A DDI as in claim 1, further comprising atleast one overload mechanism configured to, in response to at least afirst threshold force, stop rotation of the differential dissectingmember when a force exceeding the at least a first threshold force isapplied to the differential dissecting member.
 20. A DDI as in claim 19,wherein the at least one first overload mechanism is further configuredto stop the motive source in response to the force that exceeds the atleast a first threshold force.
 21. A DDI as in claim 19, wherein atleast a second overload mechanism is configured to respond to a forceapplied in a proximal direction onto the differential dissecting membersuch that when the force exceeds at least a second threshold force, thesecond overload mechanism withdraws the differential dissecting memberproximally away from the complex tissue to be dissected.
 22. A DDI as inclaim 21, wherein the at least second overload mechanism comprises: aninner sleeve aligned substantially parallel to the central longitudinalaxis of the handle; an outer sleeve aligned substantially parallel tothe central longitudinal axis and shaped such that the inner sleeve canslide inside the outer sleeve in a direction substantially parallel tothe longitudinal axis of the handle; and wherein inner sleeve isconfigured to slide proximally relative to the outer sleeve to load aspring that resists sliding of the inner sleeve relative to the outersleeve.
 23. A DDI as in claim 22 further comprising: a first spring stopaffixed to the inner sleeve; a second spring stop affixed to the outersleeve; and a spring positioned between the first spring stop and thesecond spring stop such that sliding of the inner sleeve relative to theouter sleeve loads the spring between the first spring stop and thesecond spring stop to resist sliding between the inner and outer sleevethat would further load the spring.
 24. A DDI as in claim 23, whereinthe spring is a compression spring and proximal sliding of the innersleeve relative to the outer sleeve compresses the spring.
 25. A DDI asin claim 24, wherein the inner sleeve and the outer sleeve are held at apredetermined relative position when no force is applied to thedifferential dissecting member such that the compression spring ispartially compressed to an initial compression by tension in the atleast one force-transmitting member, and wherein a force associated withthe initial compression establishes the at least first threshold forceor the at least second threshold force.
 26. A DDI as in claim 25 furthercomprising a mechanism for adjusting the initial compression and thusthe at least first threshold force or the at least second thresholdforce.
 27. A differential dissecting instrument (DDI) for differentiallydissecting complex tissue comprising: a handle; an elongate memberhaving a distal end and a proximal end, the proximal end connected tothe handle; a differential dissecting member configured to be rotatablyattached to the distal end, the differential dissecting member having anaxis of rotation and comprising: at least one tissue-engaging surface;and a first torque-point and a second torque-point disposed on eitherside of the differential dissecting member; a mechanism configured tomechanically rotate the differential dissecting member around the axisof rotation thereby causing the at least one tissue-engaging surface tomove in at least one direction against the complex tissue, the mechanismcomprising: at least one force-transmitting member having a distal endattached to the first torque-point of the differential dissecting memberand a proximal end attached to a linear oscillator configured to drivethe rotation of the differential dissecting member; and at least oneoverload mechanism configured to, in response to at least a firstthreshold force, stop rotation of the differential dissecting memberwhen a force exceeding the at least a first threshold force is appliedto the differential dissecting member, wherein the at least onetissue-engaging surface is configured to selectively engage the complextissue such that when the differential dissecting member is pressed intothe complex tissue, the at least one tissue-engaging surface movesacross the complex tissue and the at least one tissue-engaging surfacedisrupts at least one soft tissue in the complex tissue, but does notdisrupt firm tissue in the complex tissue.
 28. A differential dissectinginstrument (DDI) for differentially dissecting complex tissuecomprising: a handle; an elongate member having a distal end and aproximal end, the proximal end connected to the handle, and furtherpossessing a central, longitudinal axis; and a differential dissectingmember configured to be rotatably attached to the distal end, thedifferential dissecting member having an axis of rotation andcomprising: at least one tissue-engaging surface; a first torque-pointand a second torque-point disposed on either side of the differentialdissecting member; and a mechanism configured to mechanically rotate thedifferential dissecting member around the axis of rotation therebycausing the at least one tissue-engaging surface to move in at least onedirection against the complex tissue, the mechanism comprising: at leastone flexible tension member having a distal end attached to the firsttorque-point of the differential dissecting member and a proximal endattached to a cam follower; a torque-resisting means operably connectedto the differential dissecting member; a cam shaft associated with theproximal end of the at least one flexible tension member, and configuredto engage a cam follower; a motor operatively associated with the camshaft such that rotation of the motor turns the cam shaft; a powersource for the motor; an omnidirectional control switch operativelyassociated with the motor and the power source, and wherein theomnidirectional control switch is configured to be accessible fromsubstantially any direction; a tissue-force-limiting spring, operativelyassociated with, and maintaining a non-zero tension of, the at least onetension member; and wherein the at least one tissue-engaging surface isconfigured to selectively engage the complex tissue such that when thedifferential dissecting member is pressed into the complex tissue, theat least one tissue-engaging surface moves across the complex tissue andthe at least one tissue-engaging surface disrupts at least one softtissue in the complex tissue, but does not disrupt firm tissue in thecomplex tissue.
 29. A differential dissecting instrument (DDI) fordifferentially dissecting complex tissue comprising: a handle, having acentral, longitudinal axis; a distal end of the instrument configured tobe pointed at the complex tissue, and a proximal end of the instrumentconfigured to be pointed at a user; an elongate member having a distalend and a proximal end, the proximal end of the elongate memberconnected to the handle; a differential dissecting member rotatablyattached to the distal end of the elongate member, the differentialdissecting member having an axis of rotation and comprising: at leastone tissue-engaging surface; and a first torque-point, the firsttorque-point disposed to a first side of the axis of rotation of thedifferential dissecting member; a mechanism, configured to mechanicallyrotate the differential dissecting member around the axis of rotation,thereby causing the at least one tissue-engaging surface to move in atleast one direction against the complex tissue, the mechanism comprisingat least one force-transmitting member possessing a distal end and aproximal end, the distal end being attached to the first torque-point ofthe differential dissecting member; and the proximal end of the at leastone force-transmitting member attached to a motive source; and at leastone overload mechanism configured to respond to a force applied in aproximal direction onto the differential dissecting member such thatwhen the force exceeds at least a first threshold force, wherein the atleast one overload mechanism is configured to stop rotation of thedifferential dissecting member, wherein the at least one tissue-engagingsurface is configured to selectively engage the complex tissue such thatwhen the differential dissecting member is pressed into the complextissue, the at least one tissue-engaging surface moves across thecomplex tissue and the at least one tissue-engaging surface disrupts atleast one soft tissue in the complex tissue, but does not disrupt firmtissue in the complex tissue.
 30. A DDI as in claim 29, wherein the atleast one force-transmitting member is a connecting rod.
 31. A DDI as inclaim 29, wherein a rotation of the differential dissecting memberimparted by the at least one force-transmitting member iscounterbalanced by a counter-torque about the axis of rotation.
 32. ADDI as in claim 31, wherein the counter-torque about the axis ofrotation of the differential dissecting member is supplied by a torsionspring configured to resist the rotation imparted to the differentialdissecting member by the at least one force-transmitting member.
 33. ADDI as in claim 29, where the at least one force-transmitting member isa tension member.
 34. A DDI as in claim 33, wherein a proximal end ofthe tension member terminates on a cam follower.
 35. A DDI as in claim33, wherein the tension member is a cable.
 36. A DDI as in claim 33,wherein the tension member is formed of a flexible tension member, suchas a wire, string, rope, tape, belt, or chain.
 37. A DDI as in claim 33,wherein the tension member comprises a single, continuous tensionmember, such as a loop.
 38. A DDI as in claim 37, wherein the single,continuous tension member has a first end and a second end, and wherethe first end of the single, continuous tension member forms theproximal end of the at least once force-transmitting member, and wherethe second end of the single, continuous tension member forms theproximal end of a second force-transmitting member.
 39. A DDI as inclaim 29, wherein the motive source is a cam shaft driven by a motor.40. A DDI as in claim 29, wherein the differential dissecting memberfurther comprises a second torque-point disposed to a second side of theaxis of rotation of the differential dissecting member, providing acounter-torque on the differential dissecting member.
 41. A DDI as inclaim 40, wherein a spring is attached to the second torque-point of thedifferential dissecting member, wherein the spring is configured toresist the rotation imparted to the differential dissecting member bythe at least one force-transmitting member.
 42. A DDI as in claim 40,wherein the counter-torque is provided by a second force-transmittingmember comprising a distal end and a proximal end, the distal end beingattached to the second torque-point of the differential dissectingmember, forming an opposed pair of force-transmitting members.
 43. A DDIas in claim 42, where the first and second force-transmitting memberseach terminate on their respective proximal ends in a respective camfollower on a cam shaft.
 44. A DDI as in claim 43, wherein the camfollower of the first force-transmitting member and the cam follower ofthe second force-transmitting member both engage a single cam shaft. 45.A DDI as in claim 44, wherein the single cam shaft comprises a firsteccentric cam configured to engage the cam follower of the firstforce-transmitting member and a second eccentric cam configured toengage the cam follower of the second force-transmitting member; andwherein the cam shaft possesses a central axis of rotation, and whereinthe first eccentric cam and the second eccentric cam are arranged aboutthe central axis of rotation one hundred and eighty degrees from eachother, such that when the cam shaft rotates, the cam follower of thefirst force-transmitting member is most proximal while simultaneouslythe cam follower of the second force-transmitting member is most distal.46. A DDI as in claim 42, wherein the opposed pair of force-transmittingmembers are flexible tension members.
 47. A DDI as in claim 29, whereinthe motive source is a linear actuator.
 48. A differential dissectinginstrument (DDI) for differentially dissecting complex tissuecomprising: a handle, having a central, longitudinal axis; a distal endof the instrument configured to be pointed at the complex tissue, and aproximal end of the instrument configured to be pointed at a user; anelongate member having a distal end and a proximal end, the proximal endof the elongate member connected to the handle; a differentialdissecting member rotatably attached to the distal end of the elongatemember, the differential dissecting member having an axis of rotationand comprising: at least one tissue-engaging surface; and a firsttorque-point, the first torque-point disposed to a first side of theaxis of rotation of the differential dissecting member; a mechanism,configured to mechanically rotate the differential dissecting memberaround the axis of rotation, thereby causing the at least onetissue-engaging surface to move in at least one direction against thecomplex tissue, the mechanism comprising at least one force-transmittingmember possessing a distal end and a proximal end, the distal end beingattached to the first torque-point of the differential dissectingmember; and the proximal end of the at least one force-transmittingmember attached to a motive source; and at least one overload mechanismconfigured to, in response to at least a first threshold force, stoprotation of the differential dissecting member when a force exceedingthe at least a first threshold force is applied to the differentialdissecting member, wherein the at least one tissue-engaging surface isconfigured to selectively engage the complex tissue such that when thedifferential dissecting member is pressed into the complex tissue, theat least one tissue-engaging surface moves across the complex tissue andthe at least one tissue-engaging surface disrupts at least one softtissue in the complex tissue, but does not disrupt firm tissue in thecomplex tissue.
 49. A DDI as in claim 48, wherein the at least one firstoverload mechanism is further configured to stop the motive source inresponse to the force that exceeds the at least a first threshold force.50. A DDI as in claim 48, wherein at least a second overload mechanismis configured to respond to a force applied in a proximal direction ontothe differential dissecting member such that when the force exceeds atleast a second threshold force, the second overload mechanism withdrawsthe differential dissecting member proximally away from the complextissue to be dissected.
 51. A DDI as in claim 50, wherein the at leastsecond overload mechanism comprises: an inner sleeve alignedsubstantially parallel to the central longitudinal axis of the handle;an outer sleeve aligned substantially parallel to the centrallongitudinal axis and shaped such that the inner sleeve can slide insidethe outer sleeve in a direction substantially parallel to thelongitudinal axis of the handle; and wherein inner sleeve is configuredto slide proximally relative to the outer sleeve to load a spring thatresists sliding of the inner sleeve relative to the outer sleeve.
 52. ADDI as in claim 51 further comprising: a first spring stop affixed tothe inner sleeve; a second spring stop affixed to the outer sleeve; anda spring positioned between the first spring stop and the second springstop such that sliding of the inner sleeve relative to the outer sleeveloads the spring between the first spring stop and the second springstop to resist sliding between the inner and outer sleeve that wouldfurther load the spring.
 53. A DDI as in claim 52, wherein the spring isa compression spring and proximal sliding of the inner sleeve relativeto the outer sleeve compresses the spring.
 54. A DDI as in claim 53,wherein the inner sleeve and the outer sleeve are held at apredetermined relative position when no force is applied to thedifferential dissecting member, such that the compression spring ispartially compressed to an initial compression by tension in the atleast one force-transmitting member, and wherein a force associated withthe initial compression establishes the at least first threshold forceor the at least second threshold force.
 55. A DDI as in claim 54 furthercomprising a mechanism for adjusting the initial compression and thusthe at least first threshold force or the at least second thresholdforce.